Is the external monitor actually on/in use? Others are suggesting disabling suspend on lid close but from my experience with Debian-based distros they usually do a pretty good job these days of distinguishing between docked-lid-closed (no suspend) and undocked-lid-closed (okay to suspend). So it sounds like it might be a Fedora-specific issue if that’s the only thing that fixes it.

It’s anecdotal but (on Linux at least) Steam in 4K locks up and the driver appears to crash with Auto but does just fine with the reserved 4GB.

That’s what the instructions say to do anyway.