Fitotrack sadly doesn't connect to my Polar H10, but the interface is much nicer than open tracks or runnerup in my opinion.
Liftlog is another fitness app that is a simple weightlifting tracker and is very beautiful UI-wise though it isn't available of FDroid sadly, but the play store.
Gadgetbridge I believe is more of a replacement for the apps of respective smart watch devices and then integrates with things like FitoTrack and Open tracks via manual exports. I think it also gives trends and stats, but I can't remember, it has been a while.
This is similar to what I do.
I have a USB drive with the whole bootloader + decryption keyfiles on it. I remove it while it is running as everything is stored in RAM and already booted.
Downside being it has to be plugged in to update the boot partition during an upgrade.