I have checked 3-4 mobile-workshop-style mods. From what I could tell they are not full settlements.
Correct. They have limitations, particularly with sharing of supplies.
I believe that Annex The Commonwealth mod is fully-compatible with Sim Settlements, though I’ve not looked into it yet.
It is. I have never tried city plans with it.
Not even all mods that add a settlement to a given location will work correctly if the mod author didn't set it up properly.
This is key. The portable settlements mods can't be set up correctly. Many settlement mods on the Nexus are not.
If I remember correctly Ragoda's settlement mods don't work properly with Sim Settlements (but I could be wrong on this, I'd verify with
@Yagisan).
They were not set up properly and broke the base game. Myself and
@Rylasasin IIRC tried to help him fix them. The response we received was banning from his mods, so as far as I am concerned, all of his mods are to be considered broken, and I will never make city plans for them.
Yagisan has done a whole series of RotC city plans for custom settlement mods and he keeps a running list of mods that work and ones that don't on his
Github page.
Thank you, although it's just mods that work, that I have made plans for. There are some that do work - but I haven't released plans yet, so they are missing from the list. I need to update that documentation. I should detail discovered quirks for them, not just that they work. Perhaps after work tonight ...
I've been running the Northern Springs mod for a couple months. The author set up a settlement area just outside the F04 map. Settlers will not go up there on their own, and you cannot send them there. Setting up an IDEK station doesn't work. You can start the building foundation, but it will sit.
That is a shame. That had 3 settlements for me to check out.
Something to keep in mind - landscape and beautification mods often break third party settlements. Texture replacers work fine, but mods such as Boston Natural Surroundings just overwrite the changes needed to make new settlements work. I've released patches for the settlements I maintain, but others need load order adjustments