All I did when it turned gray was clicking the close button of the Minecraft window. This seems to be 100% reproducible in my environment, and does not happen randomly, from what I can tell (so it doesn't look like a duplicate of MC-213788 to me).
No.
I did.
Interestingly my driver was indeed outdated, I have version 10.18.10.5069 now.
I started the game with the official launcher (there should be no that big behavioral differences between that part of MultiMC and the official launcher) and the new driver, getting the same messages.
I would call OpenGL errors bugs. It's not like I need support or something... but this bug MAY get worse and cause bigger issues than simple warnings.
WifiManager wifimanager = (WifiManager) context.getSystemService(context.WIFI_SERVICE);
Method method = wifimanager.getClass().getDeclaredMethod("isWifiApEnabled");
method.setAccessible(true);
boolean wifiEnabled = (boolean) method.invoke(wifimanager);
Actually, there's more to it. It does not happen in a few other worlds with different seeds, only in this one.
Recreating the world does not reproduce it either. I attached the world that reproduces it.
A screen recording: https://youtu.be/-487ga2p-H8