OP, since we talk about android Decentralized Exhange Bisq's app, I think it will be nice to talk about what's the best Android ROM for privacy cause I think that it's not a good idea to install Bisq app on Xiaomi and call it a day
To say it briefly, I've heard that even though it sounds ironical, Google Pixel is the best smartphone for privacy because it's the most pure form of Android and you can install GrapheneOS on it.
To be honest with you. The best Smart phone for Privacy is not having a Smart phone. Graphene OS is good. But to stick to the latest Security updates, you will have to spend a lot of Money every few years as newer Pixel phones become supported while older models become obsolete. If you ask me, that amount of Money is better invested in a powerful Linux laptop or in Bitcoin itself.
There are other ROMs such as Lineage OS which are better than the stock Operating System delivered on the phone. But I do not know if Lineage OS officially supported means better Security than a stock ROM. Particularly when you now have tools that remove bloatware too through ADB and a lot of other options to improve your Privacy. And at the end of the day it all depends on what your needs are and what level of Privacy you need. Why do you not like Bisq installed on a stock Xiaomi phone? Is it because you believe a Xiaomi worker will steal your Bitcoin? Is it because you are paranoid about being spied on by China? Graphene is in my opinion too complex for the average person. If you are dealing on Bisq often then it may be a good idea. Other wise, even if other choices are still better than stock ROMs, they are many miles away from a Linux install.
You can also get a Linux phone. It is in my opinion way better than a Pixel with Graphene OS, particularly because some of them have physical switches for cameras, microphones, wireless et cetera. And removable battery too, and it can even run Android software from within. But they are extremely expensive, slow or buggy, I do not know how much Security you get on these et cetera. I still see it as an ongoing experiment.
And the worst of it all, worse even than a Temu 'Galaxy 26S' are Custom ROMs that are not officially supported but community made. But people still use them.
The idea is. Pretty much all Smart phones are more or less the same when it comes to Privacy. There are ways to improve it but it will not do any miracles. If you need real, full Privacy then not running Bisq on a Smart phone with 100 different kinds of sensors that continuously communicate with the external world is the first step to take.
