I’ve found this is a problem with my friends and myself, that any addons you try to install by downloading them from websites and importing them into your addons folder don’t work. New or old, they won’t work at all. Changing the info.txt file to addon.txt didn’t work, changing to addons.txt didn’t work. Nothing manually installed works anymore.
I know that there’s the workshop, but there’s way too many good mods out there that aren’t supported anymore by the creators, and now those mods will doubtfully be usable again if the game stays like this.
I’m not sure if this was intentional, but it wasn’t mentioned that only Workshop addons work now.