I don’t think logseq has fully automated synchronization, at least it didn’t when I started using it. What it does have is the option to automatically git commit changes. You can then synchronize through a remote repo. It isn’t fully automatic and requires a remote repo you can trust with your data but it works great for me

Something similar already happened when bicycle manufacturer VanMoof went under. I believe there was a workaround if you extracted your bike’s crypto keys before the servers went down but otherwise you were practically screwed.