Have been there lately, the repo has been archived and is read-only. This doesn't look good. Time for me to visit the Syncthing forum to see what's going on.
Edit: Looks like nel0x repo has been archived for 19 days https://forum.syncthing.net/t/does-anyone-know-why-syncthing-fork-is-no-longer-available-on-github/25661/216
Looks like nel0x and researchxxl will combine forces and maintain syncthing-fork together. Good stuff