Since sonos is a horrible fit for ST are there any audio/video systems that will interact well with ST?
What are you trying to do with your a/v system? Notifications? Or are you trying to control what is playing and whatnot? If the later, ST isn’t really designed for that. There are DTHs out there for Kodi and some other media players but they don’t work very well. Maybe things have changed in the STSC (new app) environment but in ST Classic this really isn’t a “thing”.
As @Ryan780 mentioned, smartthings is not good at stuff like playing a particular playlist or selecting individual songs.
There’s a third-party app that used to be called “roomie remote” and is now called “simple control” that lets you use both smartthings and Home theater equipment, but it’s complex and expensive with an annual fee. Some people really like it, so it may be worth looking at if you don’t mind the fees. It was designed from the ground up for people with very fancy home theater systems.
If On the other hand, all you want is to have spoken announcements triggered from SmartThings events, the Amazon echo device works surprisingly well.
If you’re looking at cameras, there really isn’t any good camera integration. Arlo has an official one but it’s pretty limited. There are people who have cobbled together various kinds of camera systems so you can search the forums for that, but they’re relying heavily on the third-party camera system for most of the features and work.
You’re right: Sonos and SmartThings don’t play well together! I love my Sonos gear and use it stand-alone or with Alexa integration only.