I was trying something, installed a few mods, and got a crash report stating that the mods required Fabric API. After installing Fabric API, I found that I couldn't launch the game again. I checked the latest log and saw that OptiFabric and Fabric API are not compatible with each other.

Use Fabric API 0.76.1+ instead of 0.77.0+. If this solves your issue please close this ticket.

i got the same problem but instead of the fabric api conflicting, its immersive portals

i got the same problem but instead of the fabric api conflicting, its immersive portals

Please open a separate ticket so that you can get support for your issue.