« Volla OS » is something that preserve the security and managed all parts of the Volla's phone. It's good to be able to reinstall this OS. I would test the other OS, like Droidian, Ubuntu Touch, …
What's the best/solution to change the OS without too many headaches, order the « Volla X » with « Volla OS » or « Ubuntu Touch », or something else ?
I've seen the thread about
Android Boot Manager - One phone to start them all!
which supports « Android 9 » only. I suppose that the last version of « Volla OS » is based on « Android 10 », so the thread is not useful at this moment.