It might be a good idea to talk to a recruiter about this. Surely there are jobs they know of where they just need people to show up and keep the fort running. That's probably what I'd do. The reason I think that's good is that companies that you would be looking for would not be easy to find in job boards because the flashy big-spend ones would show up the most. A recruiter would have easy access to the other ones, and might be happy to find somebody who actually wants to take them.

FWIW I had never used recruiters until I accidentally answered a call a few years ago, and I got my last two jobs through them and they were both awesome and the whole experience was great. Not all recruiters are like that though, so don't put up with a bad experience.

I would just send out unsolicited applications to companies, maybe under the title "DevOps Specialist", and then simply explain what you've explained here.

Like, pretty much any dev team will have a need for someone who enjoys that kind of thing. Usually, it's done out of necessity and everyone would rather work on feature development.

Legacy infrastructure code?

I don't know if this will actually work out for you--but when I did tech support, I noticed that there's a lot of little companies out there making extremely niche products and charging out the ass for them because they're SO obscure and niche, but for the people who need it, they NEED it and like to stay with the weird old niche company's software to avoid migrations and such which are considered big headaches for non-tech companies. And it's those niche products that have weird-ass old code that depends on the most obscure things. And they'll have one or two old programmers that know their shit forwards and backwards on staff--but if one retires or whatever, then they desperately need a replacement with that same mindset of keeping the old stuff running instead of chasing the newest trends.

Maybe target the manufacturing sector--companies building physical machines that need software to control them and have to roll their own in-house stuff? Or the medical sector? Or maybe something like traffic light programming or other infrastructure that will require some niche in-house software being rolled to run really old industrial or infrastructure machinery?

Like, maybe target the non-tech sectors that still have some weird in-house thing that needs to be maintained. Or look for software companies that target those markets and produce one really weird bit of software that maybe only 1,000 customers use but are charged like $25,000 a user seat or something for.