Own router to bypass IP router

I want to implement IPv6 in my home network. I found out that the router my IP provides suck for IPv6 so I figured that I'd bridge my own router. Before doing so I bought a Protecli mini pc and installed opnsense for testing with non-essential hosts. I got it working even with PXE and WoL. While I appreciate that it gets updated very often, it also implements new features and changes. I wouldn't want to keep up with changes for a backbone item as a router. My question is, is there another router OS that I could use? I guess I'm asking what is the Debian equivalent for routers? Old software but stable. If there's another subreddit I should had posted this instead, please lmk.