For anyone still following this, I’ve been working on Matter-based integration for Xiaomi and Roborock devices using SmartThings Edge drivers, based on the matterbridge project.
It doesn’t depend on the old SmartApps, and SmartThings Matter support seems stable enough for basic functionality. I’ve tested it with Roborock vacuums, but expanding it to other devices like humidifiers or fans should be possible in theory — provided they have Matter or can be bridged.
If anyone’s interested or working on similar drivers, feel free to connect — happy to share experiences or code references.