That is a good question and I was looking at Discourse initially but couldn't get it to work how I would have wanted. It also throws countless errors and seems more hacked together than a thought through software. The docker image was not really working, this may also be an error on my part but they officially don't support docker as an install method which I thought was a red flag.
I came across NodeBB in my research for a modern forum software. Looked promising. They provided a clean docker install method. I also noticed that Netgate (the company behind pfSense) uses NodeBB for their forums.
It also looked easy to maintain, which turned out true, so I settled on it.