My last programming job nearly 10 years ago I was working 4 days a week, and at my job before that there were 3 programmers who were 4 days a week.
Simply list it as a requirement when searching for jobs and go from there. It's all negotiable, if you work at it.
I, for one, am not talented at what I do, and have no power in any negotiation. I couldn't even negotiate salary, since I offer literally nothing no one else couldn't offer.
If the workplace mirrored the animal kingdom, I am more of the type of animal that feasts on carrion than hunts for fresh prey. Thus, I would never be able to swing such a deal.
However, I do hope those that can swing such a deal do so, so that it may systemically trickle down to us scavenger type.
If you absolutely can not relocate, then remote is a condition, and you will turn down any offer that is not remote.
If you absolutely can not take a pay cut, then a certain salary is a condition, and you will turn down any offer that is less than you currently make.
If you absolutely want to work four days a week, then part time is a condition, and you will turn down any offer that is not four days a week.
It's likewise in how I was willing to relocate 5 years ago for my first job. Because I wanted to take any opportunity and many others would pass me over. There's enough supply and enough talent on my end that I no longer need to relocate (plus I lucked out into a house. I'd need to literally triple my salary to justify moving and maintaining this kind of QoL if I was recruited into Silicon Valley), but I haven't seen the same prospects with part time, decently compensated tech work. I've looked out of curiosity due to long term plans, but it doesn't seem to be publicly advertised.
In one of my first jobs I negotiated less hours instead of a raise whenever I got offered a raise. I went from 40 hours/week to 36 hours/week to 32 hours/week in a few years.