Now that Android is holding back open source Android releases, I want to switch to some kind of Linux phone. It's a shame that there are no Linux phones with a mainline kernel that are fully functional and not extremely slow (looking at you, Pinephone and Librem 5), though.
And Halium is just a stopgap, since it essentially uses an Android kernel and drivers, meaning the kernel will eventually be EOL after the long term support for that version runs out.