You really need to push to upgrade to 3.0. Ruby 2.6 and 2.7 have passed EOL and are no longer being supported.
2. Hire a Pwn-As-A-Service to extract data from your company from the outside
3. Tell management "I told you so"
You didn't read this here
More seriously, I think the best you can do is not expect to find happiness in a setting that you don't fully control (ie your job), accept that, and look for joy elsewhere. It might be another job, it might be another hobby. Work fewer hours.
That's how I upgraded from Ruby 2.4 / Rails 5.0 to Ruby 3.2 / Rails 7.0
I've stopped looking for "joy" from work. Mainly focused on finding joy with my children and other hobbies, while working as little as possible. The job is the means to that end now, rather than the end itself. They continue to pay me and it supports the things I want to do outside of work so I am "happy" enough. The work itself is also moderately interesting and a decent challenge from a domain perspective, so it's not all bad.
I feel like the best you can do unironically is the first step I outlined: ask management to formally recognize that despite your warnings, they choose cost reduction. Have a trace of that, not just in case of problems, but for yourself: it's a great reminder that as long as you aren't in charge, it can't be your problem.