Your question is why launchd uses UDP port 69. This is basically because you've just told it to do so in the plist file, you've quoted in your question. If you're not used to launchd or similar programs on Unix-systems, it might seem counterintuitive - but this is how things are supposed to work.
Basically launchd does not start the tftpd server program at ...
Check ALF launch daemon is running
$ sudo launchctl list | grep alf
275 0 com.apple.alf
$ ps -ax | grep socketfilterfw
0 529 0:00.01 /usr/libexec/ApplicationFirewall/socketfilterfw
have restarted a few times and reloaded launchdaeamons with launchctl unload and load with:
unload firewall for editing
$ sudo launchctl unload /System/Library/...
As Ted Wrigley stated: "The key for specifying day of the week is Weekday, not WeekDay. Launchd may not recognize the capital-D keyword, and might be ignoring it."
After correcting the key, launchd is now not triggering everyday.
I needed a daemon listening on port 25 for local clients, so I still had to do the local LaunchDaemon setup on Catalina. The basic technique in the github scripts still works without having to hack around the protections. Using sudo, copy over the default one to /Library/LaunchDaemons and rename the file and change the Label value inside the file; what you ...