I apologise for the stupid question, but how long till we see 1.21?

However long it takes to get it coded right and working.

You can use this replacement（https://github.com/KaiAF/OptiFabric/actions/runs/9038284264 ）. Download Optifabric-Artifact.zip and decompress. Take only Optifabric-1.14.4-optikai.jar.

If you want to experience Optifine in the latest version of Minecraft, you can use Optikai（https://livzmc.net/optikai/downloads/ ）.