I think if you build the volume carefully, and modulate the intensity appropriately, you can hangboard with very high frequency without injuring yourself if you’re not also rock climbing.
I say that having once (due to a strange set of life circumstances which made this seem reasonable) had a ~10 week period where I front squatted to an easy max (and did back off sets) and hangboarded every weekday morning (as every coach in here faints). There were some supplementary exercises involved, but that was the gist of the program. This was during the winter, so I was ice climbing one weekend day, and Sunday was off or easy short run and homework. Obviously I came out of that extremely strong. I built a huge amount of work capacity on that strength over the summer, and built to a crag day where I sent 9×5.12 a/b in a day. I’m not saying this was the most intelligent way to get there, but it certainly worked. I was early 30s at the time, working and in grad school, so it’s not like I had early 20s recovery either.
It was, however, an obvious low point in my aerobic fitness.
If you want to read more in-depth on my madness, here’s the training beta article I wrote afterwards: https://www.trainingbeta.com/nicholas-kuhl-returning-to-climbing-after-a-back-injury/