https://bugs.winehq.org/show_bug.cgi?id=33943
--- Comment #14 from RoyT winehq@rbox.be --- I can't reproduce that on Arch. If you check the original bug description, you can see this is a visibility bug where the dropdown *is* actually populated but won't appear until you hover down a bit.
Selecting region has always worked, otherwise none of us would be able to even log in and play any Blizzard games. It's just that the region dropdown and any other dropdowns are not visible until you click and hover down over its position. Once you hover over any part of it, the complete dropdown becomes visible.
Are you saying this issue is any different on your setup?