They are probably referring to this: https://www.adl.org/resources/press-release/millions-examples-extremist-and-antisemitic-content-found-steam-new and this: https://www.pcgamer.com/software/platforms/steam-is-an-unsafe-place-for-teens-and-young-adults-us-senator-warns-gabe-newell-of-more-intense-scrutiny-from-the-government-if-valve-doesnt-take-action-against-extremist-content/
Yep, I used to sync my Obsidian vault with Syncthing but I had some trouble with it once where stuff wasn’t properly synced and led to conflicts so I switched to paying for Obsidian Sync and have been very happy with it. I was especially happy to see that now offer a cheaper tier that has enough storage if you only sync text files.