We are using access transformer in our forge version:
https://github.com/CCBlueX/LiquidBounce/blob/master/1.8.9-Forge/src/main/resources/liquidbounce_at.cfg
docs: https://mcforge.readthedocs.io/en/1.15.x/advanced/accesstransformers/
In fabric there is something similar named access widener:
https://github.com/CCBlueX/LiquidBounce/blob/nextgen/src/main/resources/liquidbounce.accesswidener
docs: https://www.fabricmc.net/wiki/tutorial:accesswideners