try to use Linux on Android phone.
Funny, that was one of my first thoughts when I saw this thread. I've installed a version of Linux on a few inexpensive Android
phones and
tablets and found it extremely useful (for a very niche purpose) and have been quite surprised how well it runs. Of course, the phone isn't natively running Linux, it's an Android app with a separate filesystem inside your user space, but it works fine for what I want. I've developed a web app for mapping/gps use and thought it would be cool to get it working without cell service. So, a very straightforward solution was to install a web server on the phone and access the web app on the localhost with Chrome.
Took some effort to get it setup, but it works and was even quite fast with the site located in internal storage. But I needed more space and put it on a 1tb sd card (something else an iPhone can't do), which still worked fine but was slower. Even then, just about the same as accessing the real web app with a cellular connection.
I really wanted to do something similar on my iPhone/iPad, but it didn't seem possible. I tried "ish" and some other web server apps, but none of them really worked for me. The biggest problem was (apparently) iOS doesn't support real background apps like Android. So, you can have a web server, but it just stops if it's not the "front" app.
Anyway, sorry to wander off-topic a bit, but it's related. I wouldn't want to do much administration or programming in linux on my phone directly, but I can ssh into it and the environment is nearly identical to a big linux server that I lease. It's nice to have that capability, if you need it, and it's a free app that anyone can install.
If a phone ran MacOS, I can see why that might appeal to some users as a replacement for a Mac Mini. But then you'd need a screen, keyboard and mouse (unlike just ssh-ing into my linux phone). Apple would have to charge more for such a phone, wouldn't they? It would be one more (completely different) device that needs to be fully supported by MacOS.