The main branch in the Flutter repo has gotten out of sync with master:
36b7798 (origin/main) fix minor spelling mistake in roadmap (#167888)
vs.
379eb57 (origin/master) Marks Linux_android_emu android_engine_vulkan_tests to be unflaky (#171141)
.

This breaks using Flutter from main, because the commit that's on main doesn't have engine artifacts for download.

Diagnosis

It looks like what happened is that #167888 accidentally targeted main instead of master, and got merged to that branch. Then a couple of other PRs have subsequently landed normally on master:

$ git log --oneline --graph --boundary origin/main...origin/master
* 379eb5768 (origin/master, origin/HEAD) Marks Linux_android_emu android_engine_vulkan_tests to be unflaky (#171141)
* 43312d1cd Roll Fuchsia Linux SDK from AinHuT0vgOelA1g7_... to 0-xqmXWc4cXzw3tfe... (#171823)
| * 36b77984e (origin/main) fix minor spelling mistake in roadmap (#167888)
|/  
o e80b19126 Marks Linux_android_emu android_display_cutout to be unflaky (#171140)

and the bot that would normally update main to match hasn't done so.

Fix

I believe the immediate fix is just that main should be force-pushed to match master again. (Then #167888 can be reworked and landed on master.) Not sure what permissions are required in order to do that.

There might also be useful changes to make to help prevent this situation. Or not ­— if it's been rare, it doesn't necessarily need any further prevention.