For other games with large modding communities Nexus Mods is often not the main site.
My favourite modding setup I have seen has to be Thunderstore with r2modman (initially Risk of Rain 2 modding, branched out to other Unity games), ridiculously simple and functional. All FOSS too.
Moddb?
Another good option, but more than two is better than just two giant ones.
For Bethesda RPGs: afkmods.com, tesalliance.org, loverslab.com (NSFW but has normal mods too). There are a bunch of small sites like these.
For other games with large modding communities Nexus Mods is often not the main site.
My favourite modding setup I have seen has to be Thunderstore with r2modman (initially Risk of Rain 2 modding, branched out to other Unity games), ridiculously simple and functional. All FOSS too.