Low-cost SSH access to server behind firewall?

So I had previously set up my home server with SSH on a high port, and did the port forwarding thing on the firewall so that I can SSH into this system from elsewhere on the Internet. It worked fine for months.

And then, it stopped working. The router didn’t have a software update as far as I can see. I re-checked everything, but I just can’t initiate a connection to the server from elsewhere on the Internet. It seems like it is filtered somewhere in the ISP’s network. I can, and possibly will switch ISPs, but in the mean time, I’m looking at other technical options. Though we use the other main ISP for work, and their uptime in the last couple years has been… less than stellar.

One option is obviously rent a VPS, and set up a VPN or something, and have the home server connect to that at startup. I can and have done that in the past, but even a low-cost VPS is $10 USD per month.

Some of the VPN providers out there have relatively low-cost multi-year deals, so I was looking at one of those. But it wasn’t clear if any of them supported what I wanted to do. I don’t really need to watch Netflix from a different region, I just want access to my server remotely.

I just wanted to see if anyone else is doing something like this. Thanks!