After no success with my CSL WLAN Adapter I tried the BrosTrend 1200 V2. Because I heard a lot of good things in this forum.
I followed the instructions on deb.trendtechcn.com/ and entered
sh -c 'wget deb.trendtechcn.com/install -O /tmp/install && sh /tmp/install'
Installation was successful (no asking of password for root rights).
Afterwards in my WFI connections I have the options of Device WLAN0 and WLAN1.
If I pick one in an existing WLAN connection and restart the RPI I cannot access the RPI after restart by WLAN.
If I create a new WLAN connection in the dashboard the device part is empty in advanced network connections.
Does anyone know what I have to do that I can use the WLAN Dongle?