Modding is supported, I don’t know where they will go. You might be able to find a copy of ACEO Mod Manager out in the bowls of this forum. It’s quite old and very much not up to date. But might just be enough to get you started. As for the Steam workshop stuff, I don’t know.
I expect that the GOG version also supports modding. (do you have a “modding” menu within the game?)
In that case, downloaded mods have to be shifted manually to the native modding folder of the game.
The only issue currently is getting the mods, as the only platform where mods are provided is Steam (expect some script mods which are on G-Drive) and Steam allows the download only when you own the game there.
Currently there are no plans to setup an independent download plattform or get the mod manager back to life.
If you are looking for a specific mod, contact the creator by a DM and may hope they share the files with you. Their steam username is normally almost the same as here in the forums
The issue isn’t the setup of such a platform. I do that for other games already. The big part is managing to get all the modders to upload their stuff there as well and keep them maintained on two places + prevent that others start sharing copies without permission.
And as the game is in final release since over one year, the motivation isn’t really there for such an effort. The GOG version is out since several months but so far I’ve only noticed 3 GOG players here. I don’t think there will be that many sales coming from there.