I reported this issue to the author of a separate mod and they informed me of the following:

It seems like Visual Overhaul is stopping the initialization of GUIs. The "Screen" class in Minecraft, by Minecraft rules, must have init run before it is rendered. For some reason VO prevents this.

Here is an accompanying client crash report that happens when Visual Overhaul is installed alongside the aforementioned mod. This issue was not present back in 1.19.2: https://pastebin.com/p6aUJUsY

Possibly related to #49, but just in case, I am creating this ticket.

Edit: This is Fabric 1.20.1, forgot to mention.

Can you test if this is fixed in the 1.20.4 version?

forge47.2.19，1.20.1，VisualOverhaul&Cobblemon，VisualOverhaul prevents the Cobblemon GUI (press M) from popping up and causing the game to crash.