It was my parental controls that were causing sites to be blocked. By trial and error I was able to regain access to sites, even though the categorisations were completely wrong, e.g. sites nothing to do with gambling were labelled as such. I was unable to solve the block on port 22, so I just purchased an ExpressVPN subscription. ExpressVPN seem to be widely considered as competent, and I can use OpenVPN, so there was nothing for me to install, just a config download. I'm reasonably happy with them so far.

Thanks for the help.

Seems we all were thinking blocked on the internet side, not on yours. Glad you found it and are back in business.

Maybe it would have been easier (cost wise) to have gotten a second wifi router/AP and given the kids access there with the parental controls and then removed the controls from your main router/AP
or
configured the main AP to only apply the controls to the kids IPs and not yours.

Don't know how your AP could be configured but that is a thought and could save you the long term cost of the ExpressVPN.

I don't want to add my own access controls because I have some notion (perhaps misguided) that the ISP will do a better job than I will of providing updates. I'd really like to leave all that to someone else, and have it happening outside of my house. A VPN allows me to do this. I've honestly no clue about how to configure a router to block adult sites. The last thing I want to do is be mucking about with lists of site addresses. A VPN subscription is a small cost compared to what that effort could entail.