It was a solution to a Lutris bug. Basically, flatpak containers can use these things called portals to gain access to specific files and directories via a file chooser rather than broad access or manually assigned access.

In this case, my wine installation was crashing because some part of it was trying to obtain a lock on a directory object, which is an unsupported feature when accessing a directory through a portal. The error message is something completely unrelated like can't draw window with a string of hex values. It took me a few hours to track down the real root cause.

Oh well. Works on my machine. Also, there's a fix on the development branch now. I made a write-up, posted it, and it's all gone. I should have known better honestly. It works great for some people but anybody can arbitrarily receive unfair treatment with no recourse at any time. I'm satisfied knowing that eventually the fix will get out to everybody eventually. It's just a shame I couldn't leave a signpost behind.