I am porting my pack "Create Conquest Arcane" ("CCA") to fabric and just added Mythic Metals. On the first load on my test world, I was presented with the following errors:

After inspecting the kubejs log (see attached) I discovers the cause comes from Alloy Forge recipes.

cca_kubejs_server.txt (The also contains lots of errors from Conquest Reforged, which are unrelated and I am working on addressing)
cca_mythic_metal_latest.log

I've used the Alloy Forge in other packs in the past and would truly love to use it now. However, these errors are interfering with working on the pack - hopefully, they will be quickly addressed so I can keep the mod!

Thank you,
CM

Hiya
As you state, this issue is indeed related to Alloy Forgery, it is in fact a duplicate of wisp-forest/alloy-forgery#98 and wisp-forest/alloy-forgery#102.
It has been resolved in the beta release of AF for 1.19.4.

I do want to note that as stated in the latter issue, there are no current plans to backport this to 1.19.2. For that reason I recommend using a bundled datapack for the Alloy Forge recipes. I believe KubeJS lets you handle this.