I don't think this is entirely accurate. Yes, enterprise coding can be really boring and mundane, but just as often it can be interesting and challenging and involve new technologies. As an entry level programmer, sure, you'll do Jira tickets and HTML fixes, but once you get just a touch of seniority, depending on the organization, you can get some neat opportunities.
Lots of enterprise coders are tasked with evaluating new technology, working on greenfields experiments, like building a Hadoop cluster or starting out an OpenStack test deployment. Other times, there are extremely specialized jobs in enterprises. I have some friends who write Erlang in enterprises, and they go home at 5, don't find the work too stressful, and have plenty of interesting problems to solve.
Yes, there's a lot of great tech to play with out there. You can do that on your own time as much as you can do that at an enterprise. Yeah, startups might be more inclined to work with this stuff, but they're also just as inclined to make a big tech mistake and end up 1 year down the wrong road.
Finally, I am not a fan of bootcamps to learn to code. I think they're fine to get you started, but I doubt you can actually make a real career out of just a boot camp. You'll need experience and a lot more real-world time to learn how things work when you're developing software with a dozen other people at the same time. It's a lot more complicated than just knowing how to write functions and use git.
Everyone I know who did a coding bootcamp and got a job, got a job doing the absolute most basic stuff imaginable: bug reports, bug fixes, testing, etc. There's a lot of stuff you won't learn at the bootcamp that needs to be done in an enterprise: compliance and governance work, requirements gathering, documentation development, CI/CD concerns, how to build and tweak a delivery pipeline, deployment stuff, provisioning stuff. There's a ton to learn in enterprise software development, and learning how to whip out a program in Ruby or JavaScript won't adequately prepare you. It may get your foot in the door, but expect another 2 years of working there before you'll be truly ready for a promotion or better job.
And, yes, ageism is a thing, but the absolute best programmers in the world tend to be over 50. They may not know JavaScript, but they can write an entire OS in assembly, and they tend to understand the hardware/software stack down to the bit. Old coders are absolutely incredible and wise. Anyone who is ageist in the valley against coders is really fucking themselves over.
I think the best bet for you is to do the coding boot camp, then go back to being a PM. Knowing how to actually write software is probably the most valuable skill a software dev PM can have: it'll make it a lot easier to understand why everything takes so damn long. It'll also make you much more appealing to a Google or a Facebook.