I dont know either. I used a seagate usb to sata adapter too and that gave me problems with large drives. Nothing on the datasheet mentioned anything, so i had an old backup external drive and swapped the drives to do my formatting/ transfer before putting the original back together
Lots of good suggestions already commented. I browse subs and communities, browse fdroid regularly and have a scroll through sourceforge/ git*/ alternativeto/ linux distro repositories now and again
One time i was really bored and just sorted projects on gitlab and github by stars and scrolled page after page finding many interesting projects. Then finding one thing makes you think of another which you can go look in to
For the dynamic ip address that you can get a free domain name from afraid or noip or maybe others and point your vpn to your domain name instead of direct ip address. Following that you can run cron job scripts to ensure the ip address that the domain points to is up to date