It's not super important to solve right now, but when I do window capture with Allegro and OBS Studio in Linux, it's almost like it's capturing MID-DRAW. It may be entirely "OBS fault". Vsync is on (though it happens both with on and off). NOTE that this "flickering" does NOT appear on my screen. Only the captured video.

I have not noticed this problem with any non-allegro games.

A picture's worth a thousand words, so here's a couple million:

Standard windowed mode Allegro. Newest version compiled from git this week.

al_set_new_display_option(ALLEGRO_REQUIRE, ALLEGRO_VSYNC, 2);
g.display = al_create_display(g.SCREEN_W, g.SCREEN_H);

I DID just notice that... it's windowed but I'm not explicitly requesting a windowed mode. I believe it ran the same way on my new Chromebook (running Linux) as well.

[edit] Display capture with OBS (which is much slower!) doesn't appear to have the problem.