RPI / Bullseye: error building Touchosc2midi

[PA3FUN]

Hi all. Some two years now that I'm using touchosc2midi on both Ubuntu 20.04.0 and Raspberry PI "Buster". For a number of reasons the RPI had to move on to "Bullseye". However, building touchosc2midi on Bullseye following instructions here doesn't work. Can anyone please help me? I know my way around Bash, but I am a complete noob on Python... Regards, Christiaan

P.S. I can make a fresh RPI/Bullseye installation available over SSH should this help