I just updated to version 1.9.0-87660767. It seems to have removed the ability to disable unified inbox. I used to be able to select my accounts from a dropdown menu at the top of the left panel, but now my inboxes are combined under All Accounts and the best thing I can find it having to hit ctrl+1/2/3 to switch through my inboxes. What happened to the original method and how can I get it back?
The account switcher is still there. It’s the small dropdown arrow at the top-right corner of the left sidebar, on the same row as the “All Accounts” heading. Clicking it gives you a menu with “All Accounts” plus each account individually, so you can view a single inbox instead of the unified one. The same list also lives under the Window menu, and the Ctrl+1 / Ctrl+2 shortcuts you found (Cmd on macOS) map to the same entries, with Ctrl+1 always being “All Accounts” when you have more than one account.
If you’re on a current build (1.24.x) and don’t see that arrow, let me know which theme you’re using — that’s the only thing I can think of that would hide it.