If that happens to you, that's both a great reminder that mindlessly copy-pasting commands from the internet is a terrible idea, and a chance to practice your restore-from-backup routine! I see no downsides.
I like obsidian specifically because you don't need to rely on some built-in sync tool. The files are right there and in a sane format, you can sync them however you want. I use syncthing for this at home, but the choice is yours
It eludes me how people pay to 'buy' something that they cannot download in the first place. If I don't have it as a file on my computer, I don't own it. You wouldn't pay to 'buy' a physical item if that meant only being able to look at it at the store, without the ability to take it home and do whatever you want with it.
Same, I know installing from other launchers on linux is possible using lutris, but since the steam experience is so smooth, I've never bothered to figure out how.
The only way to stop a bad guy with transgender research is with a good guy with transgender research