If you use the itch client, you don't have to do anything: it will update the game automatically and you are all set. Keep in mind that you have to have completed 8A to unlock Farewell.
Recent community posts
https://www.reddit.com/r/celestegame/comments/d1ogl2/the_game_wont_launch_after_the_update_on_linux/ provides a workaround, says devs are already on it according to same bug report on Steam.
I tried rolling back, last version pre-1.3 works great, upgrade and this pops up like clockwork, to the letter including the hash always exacty the same. I think the Linux version on itch misses some files?
9/9/2019 2:16:09 PM
at (wrapper managed-to-native) FMOD.Studio.System.FMOD_Studio_System_Create(intptr&,uint)
at FMOD.Studio.System.create (FMOD.Studio.System& studiosystem) [0x00005] in <0f2de739493b4f20a43a623d6fbc387c>:0
at Celeste.Audio.Init () [0x00010] in <0f2de739493b4f20a43a623d6fbc387c>:0
at Celeste.GameLoader.LoadThread () [0x0000c] in <0f2de739493b4f20a43a623d6fbc387c>:0
at Celeste.RunThread.RunThreadWithLogging (System.Action method) [0x00000] in <0f2de739493b4f20a43a623d6fbc387c>:0