Programs with hardware acceleration (?) takes several minutes to open a window

So… after digging a bit more regarding my issue, I stumbled over a GitHub Issue(s) which are showing the problem which I have also. It looks like that xdg-desktop-portal-gdk makes problems maybe connected with some D-Bus stuff. I already tried one thing from this but it didn’t helped unfortunately…
I’ll read through the others later if I have time.

If anyone has some suggestions to try, I’ll really appreciate it! Thanks in advance.

[ISSUE FOUND]

I found now the real issue behind my problem. It really is the firewall setting of a program which I use to handle network traffic better. Unfortunately, it’s a bug of the program itself so I can’t do something on my side. It’s already reported to the developers.

Thanks for everyone who tried to help me!