Comment # 3 on bug 1129246 from Ancor Gonzalez Sosa

The main reason of the problem is that the tftp service needs it socket running
to start gracefully.

We could try to fix YaST to ensure it starts the socket unit before starting
the service unit, but in fact and according to the systemd documentation[1],
making it work is the responsibility of the service. It should start the socket
if it is required for the service to run by adding the corresponding
dependencies to the systemd units. So I consider this a bug in the tftp
package. Reassigning to its bugowner.

[1] https://www.freedesktop.org/software/systemd/man/systemd.socket.html

If you are curious about some possible solutions we discussed to fix this at
YaST level (before concluding it was a tftp-server bug), see
https://github.com/yast/yast-tftp-server/pull/27