OK I downloaded https://download.sublimetext.com/sublime_merge_build_2047_mac.zip, unzipped, and ran it natively from the Downloads folder. The app started up without the changelog dialog, without a visible repo window, but with two menus (one per monitor). I don’t currently have any Spaces so can’t switch to a different Space (hence the missing window is not in a different Space). Neither cmd+` nor cmd+~ do do anything of consequence (no visible change).
When I explicitly request the changelog via the menus, the 2nd menu disappears from the 2nd monitor and now I am left with one menu. The repo window still does not appear.
If I use Show All Windows from the docked Sublime Merge app icon (or cmd+down-arrow) then the repo window does appear. So, I have no (additional) spaces but Sublime Merge does have a repo window. I just can’t make the window visible on any desktop, unless I go through the aforementioned new window process.
None of the following do anything useful in this scenario: Window > Zoom, Window > Bring All to Front, Window > Arrange in Front, or Window > the-only-listed-repo-window.
Mission Control shows the window on Desktop 2 (along with 2 other windows from other apps) but when exiting Mission Control, only the two non-Sublime Merge windows remain on desktop 2. The Sublime Merge window appears to travel to a location bottom-left of desktop 2, which is where desktop 1 is but the window is not visible on either desktop.
Maybe this is just a Mac thing and I don’t understand how windows behave.