How to dualboot oneplus 7 pro

I have an extra mobile (one plus 7 pro) lying around, it has really good processor and alot of storage I am thinking of making it *remote server* type something in which I can **ssh** into. Store my files or maybe learn about arm programming One plus 7 pro comes with its propriety flavour of android called oxygen OS, Is there any linux based OS that supports it. I think ubuntu touch may work. But the problem is that most of these opensource OS, do not work on their proprietary hardware. At least not fully Hence I want to be able to move back to Oxyge os, whenever I want. The only option i see is dual boot. But how do I dual boot. In PC you just press the boot key and the boot menu shows up, you can then boot from a pendrive. How does this work in phones