I have to admit, I have not much knowledge about modding. But is it possible to make the mod compatible with "More Useful Copper" (and maybe other modded hoes)?

The hoes need to be added to one of the item tags listed here: https://docs.jamalam.tech/right-click-harvest/tags.

This is generally something you would do using a datapack, or the More Useful Copper devs would do on their side.