For me this Android Test menu still works (LineageOS testbuild from Sep 22).
My provider doesn’t support advanced features like WiFi calling or VoLTE with my cheap prepaid mobile plan, but I can see the status info and I can see the switches for those features in the Test menu … for me they are greyed out, though … (“WLAN-Anrufe” or “Voice-over-WLAN” is WiFi calling in German) …
