Per https://uwsgi-docs.readthedocs.io/en/latest/Systemd.html#one-service-per-app-in-systemd and https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1130481 , of which I'm sure you're well aware, the conversation seems to lean towards "uWSGI provides the templates, the dependent packages need to implement them".
I'm not nearly smart enough to understand systemd or init.d, but I tried to follow the instructions. I obviously need lots of hand holding to see this through. # I ran: systemctl enable [email protected] systemctl enable [email protected] systemctl start [email protected] # I changed /etc/apache2/conf-available/radicale-uwsgi.conf: 51,52c51,52 < ProxyPass unix:/run/uwsgi/app/${_RADICALE_APP}/socket|uwsgi://${_RADICALE_APP} retry=0 < ProxyPassReverse unix:/run/uwsgi/app/${_RADICALE_APP}/socket|uwsgi://${_RADICALE_APP} --- > ProxyPass >unix:/run/uwsgi/${_RADICALE_APP}.socket|uwsgi://${_RADICALE_APP} retry=0 > ProxyPassReverse >unix:/run/uwsgi/${_RADICALE_APP}.socket|uwsgi://${_RADICALE_APP} # to reflect [email protected] After restarting Apache, the error messages change to: chdir() to /var/lib/radicale/collections chdir(): Permission denied [core/uwsgi.c line 3522] I tried changing [email protected] to: User=radicale Group=radicale ... to no effect. Apparently uWSGI is weird about permissions: https://serverfault.com/questions/872271/uwsgi-permission-denied-on-chdir-that-does-have-permissions-for-that-uid , and I haven't tried breaking /var/lib/radicale/collections to see if it makes any difference. Anyhow, this is pretty rudimentary stuff, but I hope it helps someone.
