Sources are required here. I think that Android being open source is great, and I actually run a fork of Android (GrapheneOS) which is great.
Again I am not against the Linux on Mobile initiatives. I have been trying them, and following since 2020. I stopped following a bit in the last couple years, but really, what I see is many Linux on Mobile projects that seem to focus on "having a nice UI" and supporting waydroid and being able to use the phone like a normal phone (that is, being able to call someone). And a ton of work mainlining mobile hardware, which I do respect a lot. However, I haven't seen much (or anything at all, really) around the security model.
In other words, the Linux on Mobile philosophy is really "bring a traditional Linux distro to the mobile phone". And the traditional Linux distro doesn't have a security model that works for a modern mobile phone, period.
I would argue that if you rethink the traditional Linux distro to have a modern security model for mobile phones, then it stops counting as a traditional Linux distro and it becomes a new mobile system. Which would be very hard (again, resources against Android), but seems out of topic because this is not what Linux on Mobile is.