That probably depends on your use case. But also what level are you on those other languages? How many do you think you can learn at the same time?
MicrowavedTea
I like most songs by Carla's Dreams (Romanian/Moldovan + Russian). From eurovision, Shum (Ukrainian) and My sister's crown (English+Ukrainian+Czech+Bulgarian) are pretty good. Slavic languages just sound nice in songs.
Also most pop in catalan (eg. La sortida, escriurem, Ara!).
For something rarer check out Pat Boy who sings in Mayan.
Adult second hand clothes are fine too even if you'll wear them longer than a child. There are many people who give away clothes in perfect state just because they don't wear them as much. I've had similar luck with brand new 40€ jeans and second hand 5€ jeans.
Not sure if this applies to the US but for most things you buy from a supermarket the generic supermarket brand is usually just as good or even better than the big brands. And it's usually much cheaper.
But I don't necessarily want to use my main phone as a hotspot.
Not the person you asked but I have a couple of sims by different providers that I swap between phones/sim routers when I need to make calls or use data from that carrier. Popping the sim into an old device and configuring whatever I need is super convenient.
Eh that's not really the same. And reading this thread it seems many providers (including mine) don't support online QR codes.
Until this article I thought you could swap eSIMs between phones, exactly like normal ones
Maybe about a year ago. It was an actual offer from a site I knew already and was too lazy to go and check it manually. Never making that mistake again as for months afterwards every ad I got was from this site. I now use adblock on my phone as well so I don't see anything but I bet I'd still get ads from that site if I didn't.
With a quick search it seems to be a translation specifically targeting Android 8.0 (API 26) but I only see it in the TBLauncher project. Some small details here but not sure why there is a separate translation for it https://github.com/TBog/TBLauncher/issues/90.
I've also had problems with Firefox on mobile. For some reason it's just very heavy on my phone, slower than chromium and has frozen android twice. I go back to it every now and then to see if it's changed but until then there are many browsers that support ad blockers. Kiwi works great for me
As a general suggestion then, for something easy I'd go for a Scandinavian language (Danish, Norwegian or Swedish). You only need one of them to kinda understand the others. For something harder Finnish or Estonian is interesting because of the many noun cases but not very useful. I don't know anything about Asian languages but Korean and Japanese would be next on my list.