I installed a command-line QR-code generator:
apt install qrencode
I used the following format, so the QR scanner knows what to do with the content:
WIFI:T:WPA;S:<your Wi-Fi network name>;P:<your Wi-Fi network password>;;
generating the QR image file then works like this:
qrencode "WIFI:T:WPA;S:My_Network;P:My_very_secure_Password;;" -o wifi_login.png
this generates an image file wifi_login.png with the QR encoded string.
while the option -o FILENAME or --output=FILENAME makes qrencode write the generated image to this FILENAME. - can be used to print to standard output.
The whole procedure works pretty well with MAC devices, but not with Android.
Is there anything wrong with the string, making it not Android-compatible?