it is possible to get blish hud working on kde plasma desktop enviroment using the workaround here https://gist.github.com/martinlabate/c4e6f08880a009f88dc1edaa4c6cd87a as long as you do not use the argument and instead use the exe and bat in the comments.

-provider Steam seems to have the opposite effect. The only issue i've noticed is you have to set the blish hud overlay to partial transparent and follow the setup steps very carefully or get a black screen which can make the menus hard to read at times and make the screen a tad darker though rasing the gama settings can hep with the later.

Note: The workaround relies on kde plasmas compositing settings and window rules so it does not work on gnome so far as my limited experience has been able to find. I'm not sure if there are similar settings in other desktop enviroments however.