.compact stopped working for me sometime in the last 10 hours or so.
Same for me. Last night old.reddit.com/.compact was working just fine, not anymore. Redirects to non-.compact.
Sadly it stopped working now. Well the new reddit mobile site is not too bad, except too slow somehow.
Not an app so to speak but a browser addon [1] that redirects to privacy site-specific proxies for Reddit, Youtube, Twitter and several others. Each can be toggled on/off.
Oh good point, I had not checked if that was one of the few approved addons for the mobile version. I forgot that is very limited. I do very little from my cell phone as I can not stand the UI/UX of smart phones.