LiquidProj3ct: I like this game shape. However I don't like the middle age and the fact that it have already DLCs (even if they are free), but I feel tempted to purchase it. It seems well done, with crossplatform support and universal moding support. I'll wait for a bit, I'm more interested in other hooded horse releases (those that are in the galaxy, like Terra Invicta), lets see what the future bring to us, and I will decide what to purchase.
This is very much long before the Middle Ages.
The game has "technically been available" for a year; the expansion's release is new there, but the whole thing is new to us, since child exploitation money was used to buy a year of Epic Game Store exclusivity.
It's likely quite well-done. It's led by the guy who did vast swaths of Civ3 and Civ4, as well as polish on Spore, and the great economic RTS Offworld Trading Company. (And so far it is -- not perfect, but no game is.)
Modding support: You're in luck! This doesn't use Steamworks bullshit from what I see. Looks like it implements a "mod.io" API.
Lack of other OSes on GOG is an issue. I wish GOG would speak more to why the bleeping bleep devs never do them here it seems. Something has to be off about how GOG works things for it to be so consistent.