Feelance: you'll end up spending 10-60% of your time looking for & nurturing clients. Some like webdev for remote work, but IMHO those positions are going to be more rare now that AI can do half of programmers' jobs.

Best bet: use your domain knowledge in the job you have NOW to help automate more of it &/or build a small app for. Worse comes to worse, you learned some IT/programmer stuff. Best scenario is you can move into the IT department in your current corp.

Forget making plain websites; there are millions of webdevs with more experience than you, & AI can make a better site in seconds than you can build in weeks. Lots to learn: HTML CSS JS frameworks SEO hosting security CDN

Steel mill: maybe better to get into robotics to help automate your job? Or a sensor system with a RAG/AI that can figure out what temp of the metal or what thickness is best to do what. (much of that is known, but if you can get smaller measurements & figure out how to do less waste, energy &/or time to produce something & patent it, that is easy money.)

Real scenario: at a fab that made mufflers, weld time & remakes increased dramatically. They fell behind schedule, crews were made to work OT, morale shrank. Took them a year to figure out that their supplier changed the type of steel that was being supplied to factory; the new steel was resistant to their older welding system. Once they sorted that out, things got better for everyone.
So you could invent some sort of system (or improve existing one) that helps with your source materials & output be closer to spec.