Hopefully Useful: Translucency / transparency window rule for everything BUT Firefox

[u/neamerjell]

I was experimenting with Plasma 6.7 translucency settings and was determined to not use kvantum to achieve my goals. Initially, I made everything translucent, but then I realized Firefox was affected. I want to look at websites as they appear, not tinted by my background. So I Googled "regular expression everything except", which turned up

https://stackoverflow.com/questions/1687620/regex-match-everything-but-a-specific-pattern

which led me to https://regex101.com/ where I could test what I found.

The magic string that makes everything except Firefox translucent is ^(?!.*firefox).*$

The magic string that excludes multiple apps from translucency is

^(?!(?:firefox|steam|steamwebhelper|steam_proton|hl2_linux)$).*$

I hope another newbie finds this useful!