Created attachment 142629 [details]
Screenshot of the issue

SUMMARY
Initially I have 2 layouts in my system: "us" and "ru".
When using option "Right Alt never chooses 3rd level" in Wayland session appears 2 more "empty" layouts, see attached screenshot.

When switching to the empty layouts I observe such behaviour:
1. first empty layout corresponds to "us" (English);
2. second empty layout corresponds to "ru" (Russian).

Under X11 session same option don't cause such issues.

STEPS TO REPRODUCE
0. Login to the Wayland KDE session;
1. Exec "kcmshell5 kcm_keyboard" (Keyboard KCM);
2. Go to tab "Advanced", enable option "Right Alt never chooses 3rd level" under "Key to choose the 3rd level" tree;
3. Click button "Apply".

OBSERVED RESULT
4 layouts appears - 2 correct and 2 "empty".

EXPECTED RESULT
No extra "empty" layouts should be shown.

SOFTWARE/OS VERSIONS
Operating System: Fedora 34
KDE Plasma Version: 5.23.0
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2
Kernel Version: 5.14.11-200.fc34.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 3600 6-Core Processor
Memory: 31.2 ГиБ of RAM
Graphics Processor: NVIDIA GeForce GTX 1060 6GB/PCIe/SSE2