Volla Phone 22 has dual boot now again. I have the Android version and it comes with Volla OS. Volla OS is based on AOSP with some components from Lineage OS and specific components from Volla. I have Ubuntu Touch installed on the external MicroSD card as dual boot. UT runs quite fast from my SD card, I can use it as my daily driver. In some cases I boot Android, but most of the time I use UT. It is much faster than my Pinephone with mobian.