The mod wasn't ready when I started my 2.1 run, IIRC this mod needs to be used right from the start, correct? Is there any way to add it mid save? I liked playing this mod in my older 2.0 save.

is it possible someone has made some kind of compatability mod that adds all the basic recipes for transitioning or something?

What recipes are not working? The main thing that's required is redoing existing factories to handle the updated recipes, so it's usually inadvisable to add mods mid-run unless you don't mind those kind of things, but in general it should work fine

Sorry this is more of a probing question, not something I'm having an issue with. My understanding is that this reworks the game enough that a vanilla save would be broken if it was installed midsave, and I'm just confirming this. Like itll leave my factory in an unworkable state and Idk if I want to deal with having to fix that all at the same time.

My secondary question was if someone has made a mod that adds back vanilla recipes so I could transition back into this mod.

You can disable specific parts of the mod in the settings, and re-enable them slowly to only fix a few things at a time. But no there's not a mod like that. Advanced circuits is where optical fiber starts to be introduced, which is widespread enough that it becomes a critical problem to solve, but it's not insurmountable from personal experience.

I did find this, seems like it might do what I need but it needs to be updated for 2.1. Hoping my request for a 2.1 update there gets addressed.

In general the crushed ore and coal recipes are the least problematic, since it's largely only mandatory when you've reached Vulcanus. But yeah it does help.