Files are files and filesystems are filesystems. You keep your files on filesystems.
NTFS and ext4 are non convertible - you cannot turn one into the other directly, in place. However you can take files from one and put them on another.
Yes, moving TBs does take time, sorry it is unbearable.
My wife's laptop absolutely has to work. For some mad reason I decided on Arch for it. Actually a rolling distro is not so mad. You get the latest stuff and in general issues are fixed as quickly as a LTS jobbie or you get a work around in the forums or you dig out the source and a compiler. It's no accident that the Arch wiki is an oft cited resource. Its not for everyone!
I've been looking at a similar thing for my company and Kubuntu so far is my choice and I've already ditched the LTS bit. I need to run AV and the usual corporate bollocks to pass silly tick box exercises, so my options are rather limited.
There is no perfect one size fits all distro, that's what we have rather a lot of them to choose from - they rise and fall according to natural selection and not artifice. Imagine if all computers were sold with a free/libre OS or none at all and Windows or Apples were a paid for add on. Monolithic OSs are completely deluded about being able to cater for all, without some dreadful contortions.
Anyway, back to the job in hand! If you want a LTS then you must accept older software or you use an LTS as a base and add newer stuff yourself. Most Linux distros allow you to run your own add-ons formally or informally. Gentoo has a rather nifty user patching mechanism for distro ebuilds and you can have your own ebuilds take over entirely. RPM and pkg distros can handle user packages and Ubuntu has PPAs too. I could go on. Also you can go off piste and put stuff into /opt and/or /usr/local!
Please reconsider your use of the term "unstable". I suggest you write down a list of your requirements and score them according to importance. Then grab a list of OSs and distros - all of them, don't preclude Windows and Apples: they have their uses. Then score the OSs/distros against your requirements. The scoring might be in the form of a matrix (table). I suggest keeping it simple with a score of -1 to 1 for each item (-1=dislike, 0=neutral/whatevs, +1=like)
Do a pilot project and see how that goes. Take your time. If it is for personal use then run your tests in a VM. Most modern hardware can easily run a VM or two. Virtualbox or VMware Worskstation or KVM (libvirt is a good effort)
The choice is yours. Note that word "choice" - its very important.
"I understand that Canonical has every right to make the decision about their product."
That seems fair. There are loads of distros available so why not try something else if you don't like Ubuntu?
Linux and other mainstream Unices such as FreeBSD or OpenBSD int al (that's not something I ever thought I'd be able to say a few decades back) are not Windows or Apples or whatevs. You do you and not them!
If Ubuntu fails to scratch your itch then move on. Debian is the upstream for Ubuntu so you'll probably be fine with that instead. There is loads of documentation for Debian via the wiki etc and of course most Ubuntu docs will apply as well.
I've just moved my work PC from a cast off from a customer - it had a BIOS date stamped 2012, and was a rather shag Lenovo with a ... Intel Core something and four GB RAM. Cheap though, ie free. I did wedge in a SSD to make it usable.
I run KDE which isn't known for being tiny and I have a Postgres DB and a few containers for experiments running. The new box is a i5 Intel G13 thingy - HP mini jobbie. Luxury
To ensure that I am as disadvantaged as everyone else, I run ESET Endpoint AV and full disc encryption on it. It boots EFI and Secure Boot is enabled. I will pass a Cyber Essentials Plus audit (UK standard) without having to employ any misdirection. I've also read up on the US standards. The STIG for Ubuntu 22.04 is doable but my desktop is running 23.04 and 24.04 has just come out.
I run my company and we have some customers who have some rather more stringent requirements than others. We also have our own standards.
I feel like I’m the only person who can’t make heads or tails of
It doesn't matter if you get the result you want. The important thing is you have choice and that what you have chosen ... works!
They don't need a new distro, unless they hire a lot of highly skilled packagers. I'd take say Ubuntu or OpenSuSE ... but it would be RedHat with Oracle for the NHS - they just can't help losing money.
For my tiny company, I'm going Kubuntu ... bear with ... Ubuntu means:
Those boxes ticked gets you on the way in the rather naff enterprise security word of tick boxes. Without those - give up now.
The K(DE) bit gets you a lot of configurability and its reasonably easy to get an environment out of the box that Windows users can get to grips with. Besides, I like KDE/Plasma.
I then tack on this rather fine project: https://cid-doc.github.io/ for AD, SYSVOL, "Drive letter" etc integration. Evolution with EWS does email.
My test machine is my desktop (it used to run Arch (actually), my laptop still does) - I started off with Kubuntu 22.04 and wired up all the above and then whilst in a Teams meeting kicked off the upgrade to 23.04 for a laugh. Sound stopped after a while because the kernel modules switched out. Anyway, all good after a reboot.
Seeing as I am competing with something that has GPO, I'll allow myself to use Ansible.
PS - I should point out that an Arch box can run one of the ESET for Linux products OK (I have). You can get it to do secure boot and it can do FDE. So can Gentoo but I spent 15 years constantly fixing my Gentoo pets too.
I (my little company) employ a bloke to support https://www.uzerp.com/ - we use it ourselves and ditched Sage (yay!)
If you fancy it then give us a shout - it is open source - you get it for free but our time is costed if you need assistance.
That is the Open Source Covenant
I do use it quite a lot. The pfSense package for ACME can run scripts, which might use scp. Modern Windows boxes can run OpenSSH daemons and obviously, all Unix boxes can too. They all have systems like Task Scheduler or cron to pick up the certs and deploy them.
I do IT security for a living. It is quite complicated but not unrealistic for you to DIY.
Do a risk assessment first off - how important is your data to you and a hostile someone else? Outputs from the risk assessment might be fixing up backups first. Think about which data might be attractive to someone else and what you do not want to lose. Your photos are probably irreplaceable and your password spreadsheet should probably be a Keepass database. This is personal stuff, work out what is important.
After you've thought about what is important, then you start to look at technologies.
Decide how you need to access your data, when off site. I'll give you a clue: VPN always until you feel proficient to expose your services directly on the internet. IPSEC or OpenVPN or whatevs.
After sorting all that out, why not look into monitoring?
I think we might be writing at cross purposes. The system you had for your mum obviously worked effectively for you and that is the important thing.
POTS provide(s|d) a fixed point of reference - your address is registered against the number for 999 etc; it provides power for a handset or device; Its been like that for a lot of decades! These are cast iron guarantees. A POTS line has guarantees, enshrined in UK law, that mobile etc does not have. POTS is circuit switched (well it was) which means there is a physical path between the ends for the duration of the conversation.
So, by old school, I mean that you currently have important guarantees about telephony in the UK that will evaporate in future. In 2025 or so, we in the UK will have finished migrating from our old school POTS copper lines and will enjoy our smart new SoGEA lines instead. Single Order Generic Ethernet Access. Instead of an emulated circuit switched line we will use VoIP across the entire country. Nothing wrong with that but it probably won't have the guarantees that POTS had.
Red Care is no more - BT have dropped it on the floor as of Feb this year which may indicate that things are not well with our future comms promises. The general system that Red Care was one product of is still available.
This is the important point: Promises (in law) that we used to be able to rely on for comms may (will) be binned.
In the UK at least, the POTS (Plain Old ...) copper phone lines carry an electrical current as well as signals and can power the handset. There are certain guarantees about this so that in an emergency your phone will still work so you can dial 999 (our original emergency number) or 112. Our fire regulations require something like 30 minutes before things should start failing. In the real world, you get out immediately and use your mobile.
We have an emergency alarm monitoring system used by businesses. Its generally known as "Red Care" which was a brand run by BT (British Telecom). You have a small device connected to a phone line (and powered by it) and it will monitor your fire detectors and building access control systems and a 24 hour manned monitoring centre will notify you in the event of an emergency. Nowadays, these devices will use your wifi and internet connection. Sometimes: old school is best.
Rustdesk is pretty decent and being developed quite fast. Why not look at MeshCentral too. Choice is good and MC has been around for a fair old while.
My company replaced Teamviewer with MC and we have thousands of client machines across the UK.