This is a request, not a bug.
The lower versions of forge/fabric are rarely updated now, and only require one migration to be effective for a long time.
For example, versions 1.16.5 and 1.12.2.
I have now gotten used to installing this mod in any high-version mod-packs to significantly improve performance. This mod has become a necessity for me to play MC. LOL.
If necessary, I can pay you to port the lower version.
My English is very poor, the above content is from the google-translation.

I don't have much interest or motivation to backport the mod to 1.16 or 1.12. It would basically require a rework of all of its patches and optimizations. They've changed a lot over the versions, and the main version I develop for is whatever is newest.

As for 1.12 especially, I don't think forge supports mixins below 1.18.2 so that wouldn't even really be feasible.

Okay, thanks for your quick reply.
If there is really no hope, forget it.
What a pity. TAT