Hello again.

Assuming the fuel cat change is what did it. Per the changelog:
- Replaced ItemPrototype::fuel_category with ItemPrototype::fuel_categories.

But on load ...al-chemistry__/prototypes/final-ui-totalraw-contract.lua:996: RIC 0.35.28 Factorio 2.1 fuel API contract failed: still uses removed fuel_category; use fuel_categories

Stack traceback:
[C]: in function 'error'
...al-chemistry__/prototypes/final-ui-totalraw-contract.lua:996: in main chunk
[C]: in function 'require'
real-industrial-chemistry/data-final-fixes.lua:124: in main chunk

Though maybe it's the base AAI indy mod. Tried it with just AAI indy on + base game and also errors out. Not sure if it's something you both need to address so thought I'd post it here anyway.

Though doesn't seem to as it YOUR mod loads without AAI running. But the loading screen wants to disable "Real ore" mod. If already fixed on your end / not something you can control all good. Just thought I'd say something.

fixed it so it doesn't stop against other mods not updated for this 2.1.20 change

Thanks! Do you know why the devs changed that? Seems odd to change the wording in the code and break everyone's mods. But I also don't know coding.

no idea

Ah, well no worries then. TY.