Playing on pc, I can play 1.16.1 just fine on MULTIMMC5 as long as I dont add Optifine 1.16.1 and Optifabric. Ive looked at tutorials as to where they go but they dont actually specify which Mod folder in the Multimmc5 directory I should put them.
According to OptiFabric they both go in the mods folder, however, in Multimc5 there are 2 mod folders. One under Instances/1.16.1 and the other is the Central Mods folder.
When I add those two files to the 1.16.1 mods folder, the game crashes. When I add them to the Central Mods folder, the game doesnt crash but OptiFabric and Optifine dont show up ingame
Have you extracted Optifine or just put it in the folder? Check the loader version or try using other Optifine versions I guess. Otherwise best to ask the OptiFabric dev in the Fabric Discord otherwise as without a crash report I have no clue. https://discord.gg/v6v4pMv