According to a developer at Gnome/evince: "The fix is included in Poppler latest release 21.06.1."

This issue does indeed seem to be resolved following the GNOME stack upgrade; it may be closed. Thank you for following up on it!

I've had a particularly difficult time post-startup after this most recent update of budgie-wm.desktop. Perhaps MetaSyncRing is part of the issue? I locked up three times in a row, until the system apparently disabled MetaSyncRing.

I don't have TLP installed, but I do have solus-hardware-config installed, which I think is the default. It may be useful to note that having version 15 or later installed activates cpu-powersave.service in the latter stages of boot, thereby transitioning "into ondemand for cpufreq systems and powersave for intel_pstate systems." I muddled through finding my own workaround here.

I can now confirm this only occurs when I open a window that's set to open maximized. This does not occur if I open the same program, so long as the window isn't maximized. This appears to be a budgie-wm.desktop and budgie-panel issue, but I'm no developer.