I actually have full development environment set up on my phone. Combine that with bluetooth keyboard/mouse combo and I am good for about 85% of the work, if not more. Helps a lot not having to lug laptop around all the time.
Can you share your setup? Is it monitor compatible? Do you carry your own keyboard and mouse? How long will yhe battery last when using with a monitor? What do you do for package management?
I have Samsung Fold4. With pen I don't need mouse, but I do have a bluetooth mouse (Logitech M720) and iClever foldable keyboard. Most of my development is done in Vim as I do server side, so Python and similar. Termux does pretty much everything I need.
I also carry USB C hub with me, which has HDMI and LAN adapter built-in, so I can further extend its use. Hub also has charge capabilities, so I can have a longer working hours. As far as external displays are concerned, I don't have any as I didn't need them really yet.
Great setup. Have you had any issues with body posture, or visibility in use? As in, do you feel like you have to strain to see stuff on the smaller screen?
I don't use it all that frequently but I have to be available pretty much 24/7. At times I did use it it wasn't much of a problem. Screen is pretty high resolution with enough high refresh rate that it feels natural. Keyboard is almost full-size so comfort wasn't a problem there either. Full desktop environment of course would be preferable but this works nicely. That can also be achieved with Android but desktop is then accessed through local VNC connection, of which am I am not a fan. Samsung's DeX is good enough for most of things, but on my device I can't activate it until I connect it to external display. Samsung's tablets on the other hand, can!
Nice; have you considered small form factor laptops, like the GPD mini-laptop or one of those box shaped mini computers? I suppose they make a lot less sense if you have to carry a seperate box around instead of just using your phone.
I explored this idea of substituting my laptop for work (its a giant ~17 incher) with either something small I can carry around with me or something I can just leave locked in my work drawer or something; so I'm excited to talk to someone who had similar ideas and made it work.
I considered many different options and foldable wasn't my first choice either. Initially I waited for Blackberry Key3, when they decided to stop making them to my disappointment. Foldable was my next choice because I really don't want to have a separate device. For a while I lugged my X1 Carbon with me, which is fairly light laptop but when you add charger and the rest of the gear it's not much lighter than any other machine.