this error is produced when attempting to load up the game with yuoki's enabled https://i.imgur.com/oHjn32e.png

disabling omnicrystal produces a different error for omnimatter https://i.imgur.com/y5kdqgN.png

disabling Yuoki's lets the omnimods work perfectly. (did not test omniscience)

i'm not sure why this happens since you previously added support for Yuoki's

I had the same error. Line 57 of data-updates.lua is trying to set the icon.

rec.icon=data.raw.item[plate].icon

I changed data.raw.item[plate].icon to "omnimatter_crystal/graphics/icons/omnide-salt.png" and the next error I received was this:

Failed to load mods: Error in assignID, item with name 'y--plate' does not exist.

Source: y-res1-omnitraction(recipe).

Mods to be disabled:
omnimatter_crystal

I got it to work.

        elseif ore == "y-res1" then
            plate = "y-crush-yres1"
        elseif ore == "y-res2" then
            plate = "y-crush-yres2"

Add that in that area (just before the final else) and it'll work, however it will smelt to the yuoki dust, it might be better to have it smelt to something else but I am not for sure what. Since the intention of this set of recipe is to go from the crystal to the final plate format. But with yuoki there's no plate-format of their two ores.