Well, that's not true. Motorola also has their own desktop mode. And OnePlus. And Xiaomi. There is probably more.
I believe it's possible for smartphones to become the only computer unit in a person's life. Smartphone + lapdock for portable work and smartphone + monitor + wireless mouse/keyboard for home work. I'm looking for a ROM (or maybe a different OS from Android, like Fuchsia OS maybe?) that brings that possible future closer.
I found MaruOS a few minutes ago, for example.
I just found MaruOS. It appears to be exactly what I was looking for. They are a little small apparently. They support only Nexus phones and one Samsung's device. Hopefully they'll have a bright future.
A quick tip.
After you have root, you can download twrp's app via google play and then install the recovery from the app. Hassle free and safe.
https://play.google.com/store/apps/details?id=com.jmz.soft.twrpmanager&hl=sv