Some further digging. The appletalk module does not seem to be the issue. However...
pi@rascsi:~ $ sudo journalctl -u atalkd.service -b
-- Journal begins at Sun 2022-02-06 21:58:35 CET, ends at Tue 2022-05-03 19:19:49 CEST. --
May 03 19:15:28 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:15:29 rascsi atalkd[448]: atalkd: zero interfaces, exiting.
May 03 19:15:29 rascsi systemd[1]: atalkd.service: Control process exited, code=exited, status=1/FAILURE
May 03 19:15:29 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:29 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:30 rascsi systemd[1]: atalkd.service: Scheduled restart job, restart counter is at 1.
May 03 19:15:30 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:30 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:15:30 rascsi atalkd[480]: atalkd: zero interfaces, exiting.
May 03 19:15:30 rascsi systemd[1]: atalkd.service: Control process exited, code=exited, status=1/FAILURE
May 03 19:15:30 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:30 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:31 rascsi systemd[1]: atalkd.service: Scheduled restart job, restart counter is at 2.
May 03 19:15:31 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:31 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:15:31 rascsi atalkd[504]: atalkd: zero interfaces, exiting.
May 03 19:15:31 rascsi systemd[1]: atalkd.service: Control process exited, code=exited, status=1/FAILURE
May 03 19:15:31 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:31 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:32 rascsi systemd[1]: atalkd.service: Scheduled restart job, restart counter is at 3.
May 03 19:15:32 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:32 rascsi atalkd[505]: atalkd: zero interfaces, exiting.
May 03 19:15:32 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:15:32 rascsi systemd[1]: atalkd.service: Control process exited, code=exited, status=1/FAILURE
May 03 19:15:32 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:32 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:34 rascsi systemd[1]: atalkd.service: Scheduled restart job, restart counter is at 4.
May 03 19:15:34 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:34 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:15:34 rascsi atalkd[506]: atalkd: zero interfaces, exiting.
May 03 19:15:34 rascsi systemd[1]: atalkd.service: Control process exited, code=exited, status=1/FAILURE
May 03 19:15:34 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:34 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:35 rascsi systemd[1]: atalkd.service: Scheduled restart job, restart counter is at 5.
May 03 19:15:35 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:15:35 rascsi systemd[1]: atalkd.service: Start request repeated too quickly.
May 03 19:15:35 rascsi systemd[1]: atalkd.service: Failed with result 'exit-code'.
May 03 19:15:35 rascsi systemd[1]: Failed to start Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:17:03 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:17:03 rascsi atalkd[705]: Set syslog logging to level: LOG_DEBUG
May 03 19:17:03 rascsi atalkd[705]: restart (2.220101)
May 03 19:17:04 rascsi atalkd[705]: zip_getnetinfo for wlan0
May 03 19:17:14 rascsi atalkd[705]: zip_getnetinfo for wlan0
May 03 19:17:24 rascsi atalkd[705]: zip_getnetinfo for wlan0
May 03 19:17:34 rascsi atalkd[705]: as_timer multiple interfaces, no seed
May 03 19:17:34 rascsi atalkd[705]: as_timer can't configure wlan0
May 03 19:17:34 rascsi systemd[1]: Started Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:17:34 rascsi atalkd[705]: as_timer waiting for router
May 03 19:17:34 rascsi atalkd[705]: ready 0/0/0
May 03 19:18:44 rascsi atalkd[705]: done
May 03 19:18:44 rascsi systemd[1]: Stopping Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:18:44 rascsi systemd[1]: atalkd.service: Succeeded.
May 03 19:18:44 rascsi systemd[1]: Stopped Netatalk AppleTalk daemon for AFP fileserver.
May 03 19:18:50 rascsi systemd[1]: Starting Netatalk AppleTalk daemon for AFP fileserver...
May 03 19:18:50 rascsi atalkd[717]: Set syslog logging to level: LOG_DEBUG
May 03 19:18:50 rascsi atalkd[717]: restart (2.220101)
May 03 19:18:51 rascsi atalkd[717]: zip_getnetinfo for rascsi_bridge
May 03 19:19:01 rascsi atalkd[717]: zip_getnetinfo for rascsi_bridge
May 03 19:19:11 rascsi atalkd[717]: zip_getnetinfo for rascsi_bridge
May 03 19:19:21 rascsi atalkd[717]: config for no router
May 03 19:19:23 rascsi atalkd[717]: ready 0/0/0
May 03 19:19:23 rascsi systemd[1]: Started Netatalk AppleTalk daemon for AFP fileserver.
So... my AFP Fileserver won't start. Why though? Is there an idiot-proof writeup on how to install this?