I have browsed this forum's mods and bugs/issues sections looking for something - and did not find it. To confirm my suspicions: Linux version does not support mods? I have no wish to destroy my working game just to colour my ingame cat to match my real one. Thank you! I did not read any posts in detail. What I did do, was scan through post titles. No 'linux bugs' mention mods in their titles, and no 'mods bugs' mention linux in theirs.
I haven't tried myself, but mods should be fine on Linux. The SMAPI thread says and searching for "Linux" in the mods forum brings up results including fixing compatibility issues for some mods on Linux. I think people are just more likely to report a Linux-specific bug for a mod in the mod's thread, rather than make a new one with "Linux" in the title.
Yes, all mods I've tried in Linux work fine. There has been an issue I've run into twice, where a mod will fail, saying it can't find the .dll named in the manifest.json file. It's a simple capitalization problem. The manifest.json is a simple text file and can be edited so the file name exactly matches the existing .dll file. Haven't seen it in a while and I think mod authors are getting on board with case sensitive OSs. TLDR: Yeah, Linux works!
Being a fellow Penguin, I can absolutely confirm that I can run heavily modded instances with the Linux version. As of SMAPI version... whatever it was when 1.2 came out... it became an agnostic program, capable of running on PC, Linux, or Mac equally well. I've reported a few minor concerns, such as the executable didn't work for a bit due to capitalizing (Linux is caps sensitive, Windows is not), but those have been fixed for well over a year now. As long as you have the current version of SMAPI to run your mods, you'll be just fine. If you can run SDV, you can also run SMAPI. I would advise against direct XNB edits, and offer Content Patcher as an alternative to the same goal, but that is less a Linux compatibility thing so much as a Steam compatibility thing (direct XNB edits are wiped when the game updates or when you Verify Integrity, Content Patcher is not affected).