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.