My opinion about tournament no-show.
If tournament is paid entry(Prepaid)
I think no-show is okay. You already paid and supported the tournament. It is better to tell organizers, but I don't think it is required.
If tournament is free entry
You can not cancel in startgg. So If you cannot come, tell organizers as soon as possible. If too late, at least post on social media and let people know, so tournament is not affected.
This basic thing.even daycare in kids also can do this lol.