Overview here

https://forum.syncthing.net/t/does-anyone-know-why-syncthing-fork-is-no-longer-available-on-github/25661/39

The new owner of the repo has a fresh github account and apparently has the signing keys from Catfriend1 too.

Time will tell if they are trustworthy, but for the extra paranoid it might make sense to pause updates for a while.