https://github.com/geoffreybennett/scarlett-gen2/pull/1
Here's the full description:
This set of patches enhances support of Focusrite Scarlett 18i20 Gen3 and other Gen3 devices.
The list of changes:
* Fixed bug that moved clients (like alsamixer) into infinite loop when changing any control in the UI.
* Added proper INST button controlling and synchronization with audio device.
* Added proper PAD button controlling and synchronization with audio device.
* Added software 48V phantom power switching support.
* Implemented proper ALT button synchronization with audio device.
* Implemented TALKBACK button support and synchronization with device.
* Added myself to the list of authors.
So there are no buttons left on the 18i20 device (except power button) that can not be enabled by software. Also software now properly handles all manual button presses and triggers client mixer software to update.