1.17 brought us:

• Java 16
• CyclingButtonWidget (net.minecraft.client.gui.widget)
• Screen#addDrawableChild

After replacing the usages of those (and being thankful for their existence in the new version), the port was fairly straightforward.
The JAR only works on Minecraft 1.16.2+, however, due to fabric-resource-loader-v0. If you need one for 1.16 or 1.16.1, tell me.