So the problem is solved?

yes, I think so.


But what was the problem?

no Linux did switch from 0bda:1a2b to 0bda:c811 when I first tried to use it in May 2020.

I had tried to trace the USB communication under MS Windows without success and had the stick sitting around on my shelf since then ...

finally I found time to revisit this problem and alas under a recent version of EndlessOS (Debian bullseye based) I see the following in dmesg output:
[ +43.654396] usb 1-3: new high-speed USB device number 6 using xhci_hcd
[ +0.148128] usb 1-3: New USB device found, idVendor=0bda, idProduct=1a2b ...

Did you try to eject the cd-rom device from linux cmdline?

yes I tried that several times without sucess.

After having switched successfully under windows, I ejected and unplugged the stick and moved it to the raspi, and now lsusb list it as c811. I have no idea how long it must be offline to ...

hmm, I tried to use sudo eject on the command line already without success, see above.

I logged the communication with USBlyzer, but I have some problems in interpreting the results. Digging through the packets, my impression is that the driver does try to eject the disc with a start/stop unit ...

I bought yet another usb wifi stick, which has 0bda:1a2b and is not switching to c811 with usb_modeswitch (see also: https://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?f=3&t=2936). It is an Inter-Tech DMG-19 and documentation says that it uses Realtek RTL-8811CU chipset
(see https://www ...