>How easy/hard is it nowadays to just go to a store, buy a nice phone, go home and put Mobian on it?

I don't want to say impossible, because that's not quite true, but close to. Mobian runs pretty much a stock Linux kernel, and there are only two recent devices on the market designed to do that: the PinePhone and the Librem 5. The alternative is to use libhybris to run on top of an Android kernel (including all the proprietary drivers needed for a typical Android phone), but... that's really something the distro developers would have to do, not you as a user.

Some Android devices are now mostly bootable with mainline Linux or something close to it (PostmarketOS has done a lot of great work here), but these are typically devices that are several years old, not the kind of thing you'd go out and buy in a store.

In short: unless the device you buy happens to be a PinePhone or Librem 5 or you are a dedicated kernel hacker or distro developer... no chance, for the vast majority of recent devices you might buy.

Would I be able to put Mobian on the phone in the first place? How would I do that? Is there a button combination or something that tells android phones to boot from an external media?

As a pinephone owner I can tell you that non android based Linux phones are years away from having a feature set that would make them acceptable for a general consumer.

I d definitely recommend the pinephone for playing with it and watching it's progress though ;)

As I said, for me it is not about the experience. I just want to run Linux on my phone and be part of the journey. If I have a working terminal, that would already be cool.

The thing with the PinePhone is that it is not very easy to buy. Say I get used to the PinePhone as my daily driver for having a terminal in my pocket. And then it breaks. Then I am f*cked and have to wait weeks or months for a new one to ship from Hong Kong.

If we were at the point were I can just go to a store, buy a phone and put Linux on it - I would start right now.

Years away? Nah. The PinePhone was literally useless as a phone at the start of the year, now I'm close to mainlining it. As long as calling/SMS/internet works it's good enough for me.