"Couldn't find current GLX or EGL context" on KDE Plasma 5.21 using AMDGPU

[frumble]

Hello, I’m using a Radeon RX 5700 XT on Arch Linux, Kernel 5.11, libepoxy 1.5.5 and after the recent update to KDE Plasma 5.21, its compositor Kwin is constantly crashing with the error log:

kwin_x11: ../libepoxy/src/dispatch_common.c:858: epoxy_get_proc_address: Zusicherung »0 && "Couldn't find current GLX or EGL context.\n"« nicht erfüllt. [English: Not fulfilled]
Application::crashHandler() called with signal 6; recent crashes: 1
KCrash: crashing... crashRecursionCounter = 2
KCrash: Application Name = kwin_x11 path = /usr/bin pid = 9100
KCrash: Arguments: /usr/bin/kwin_x11 --crashes 1

I have already filed a bug report on the KDE bug tracker. It’s especially occurring when I’m using Firefox (configured to use WebRender), Thunderbird and dragging around remote windows in the NoMachine client. Might take a couple minutes surf time but it does happen each session.
I will attach logs of "kwin_x11 --replace" running into the crashes using Firefox, Thunderbird and NoMachine and a strace protocol of Kwin until a crash happens.
I don’t understand enough of this tech to pinpoint if this is more a Kwin or libepoxy bug.

Kwin crash No 1 Firefox.txt
Kwin crash No 2 Thunderbird.txt
Kwin crash No 3 Nomachine.txt
Kwin crash strace with Firefox.txt

[frumble]

Solved by resetting Kwin config.