Very interesting.

Do you happen to know/assume/guess if this would also work with Planet mods. For example, of the ones I am currently using, Lignumis & Cerys specifically have an "incompatible with" for RSO currently.

Would be perfect to find out that this solves whatever issue they have.

Thanks for your question!

The main problem I faced: when RSO mod is enabled with custom ores that don't have RSO support built-in, those ores wouldn't spawn at all. The game world would generate without them completely.

My mod just automatically add data.rso_ignore_resource_entities if RSO not support ore

I tested with QuirkyCat ores and it works - they now spawn correctly using their default generation while RSO handles vanilla + BZ ores.

So if Lignumis & Cerys incompatibility is caused by RSO trying to control their ores and failing, this mod should fix it by telling RSO to ignore them completely. I'll test Lignumis & Cerys compatibility tomorrow and update here with results. If you test it before me, please share your findings!

Also You can check factorio-current.log after loading - the mod logs which ores use RSO vs default generation.