One of my sons had this problem until he was in elementary school. We tried to take him to the bathroom before we went to bed, limiting his fluid intake in the evening, and ll of that. Did not make much difference. I did not make a big fuss about it, but it was very obvious that HE was not happy about and it affected him.
I did an internet search and some of the things, like alarms that go off when they sense moisture did not make sense to me, as by that time it was too late, medications did not appeal to me, those would have been my last resort. I did come across info that a chiropractic adjustment might be helpful, and I figure I would give that a try. I did not see any downside to it, it was worth a shot, and if it helped all the better. My husband was quite skeptical but agreed as he did not see any down-side to it, either, and we were clearly running out of ideas helping our son with his problem.
And it was so worth it! With just a couple of adjustments he wet his bed only 2x/week (from prior to that almost every single night), and after a couple of weeks he was dry. Since then he's been dry with only one or two more accidents, and now it's been 7 or 8 years since the treatments. He was a changed kid.
Now this may or may not work, obviously, I was happy that it did work for us, but I wanted to share it as an option you might consider trying.
Best wishes!