Theoretically yeah it's compatible, it doesn't really do anything that should effect ET directly, but otherwise, I'm not 1000% sure since I don't personally use ET

One question, this mod is compatible with ET?

Interesting!

It's multiple decisions that has specific internal triggers per conversion grouping, then they slowly automatically convert using the pronoia system mechanics

Do you need to manually convert the provinces or are they mtth?

The current mods/modules coming are:
Irish-Cultures++
French-Cultures++ (already partly out as part of Core)
Cultures++ Monolith (all mods combined into a supermod)

I am actually planning on making more mods! I'm currently working on a new Irish Cultures module that should release soon, and I'm currently working on a discord server for people to post suggestions as a whole to future modules and directions.

I'm not actually sure if creating new cultures in game is possible in the current state of the EU4 codebase, but it is certainly an interesting proposal and I will absolutely consider seeing what I can do.

Are you planning on creating more mods or make it able for us to make our own cultures?

Lmfao, this originates out of a failed EE proposal, though I've been posting updates to the development on their discord if you're curious what'll be in 1.1

1.1 will finally let the new culture groups be obtainable
1.2 will add a new religion, that's the plan for the moment anyway.

the hellenic renaissance mod already does that so

Honestly, this should just be merged into Europa Expanded when they decide to replace the somewhat-dated Flavor Universalis tree with their own completely unique one. As should the series of flavor mods by RMS_Oceanic, I highly recommend looking them up.