Congrats on the new release!
I ran into an odd issue with ST4. When I have ST4 open on my second monitor and then quit the app and relaunch it, ST appears in the menu bar but the window does not appear. I tried the “Bring to Front” and “Show all windows” menu options and it still would not appear, yet strangely it appears in Mission Control.
The only way to get the window to appear again is to go to “Window > Move to (second monitor)” and the animation shows the window moving across my first monitor to the second monitor.
If I quit ST4 on my first monitor and relaunch it, the window appears immediately on my first monitor with no issues.
I am running Big Sur 11.3 on a Mac mini 2018 connected to an RX 560 EGPU and two identical LG 4k monitors.