Not MITM, but rather the application processor trusting the baseband processor, which is running who-knows-what network-facing code. Qualcomm claims to have recently implemented memory separation, but without actual public documentation and scrutiny of internals why would one believe them?

Installing F-droid does not remove Google's presence in other software. On a vanilla Android phone, that is all of the Google (Play) services and who knows what centralized-expedient hacks have been put into the OS itself.

Do you really think Google or Qualcomm are going to try and root kit servers you ssh into? Google's privacy model is awful for many reasons but this doesn't seem like one if them.

I think my computer is my castle, an extension of my own mind, and subjecting it to the mercy of unaccountable third parties is a terrible idea. I can also foresee many business reasons why they might choose to be active attackers, such as measuring the popularity of various applications and data files. The pop culture mobile ecosystem has steadily increased into a dumpster fire of authoritarian control, and it's reasonable to assume the trend will continue.

LineageOS can remove the Google problem with relatively little pain, compared to running mobile Linux.

The untrusted hardware is, of course, a more complicated matter.

OP didn't mention LineageOS or custom ROMs, but rather promoted stock vendor Android with Termux. Yes, you can do additional work to fight the top-down controls. But you're running an uphill battle, and judging by the shrinking device list of LineageOS that hill appears to be getting steeper.

Please continue fighting that fight as I am currently, but at some point it's nicer to cut bait and move to an undeveloped ecosystem where you're welcome rather than persist in a more polished one where you're not.

I would love to switch to a fully open environment once it's available, but I think you're overstating the trouble with running LineageOS or other non-spyware ROMs.

Reasons to favour custom ROMs over Linux phones as a daily driver, at the moment:

- You get to pick between dozens of recent devices, many with flagship specs. (Note that the "official" device list only refers to the ones the core team approved, there are many more that stay "unofficial" for a year or more before getting accepted, but still work quite fine.) Other ROMs like Graphene are more limited, but an old Pixel is still way more powerful than a Pinephone.

- Basically everything that a mainstream Android can do works fine on custom ROMs. Exceptions tend to be big tech stuff like Google Pay which you probably don't want anyway if you're into privacy, or occasional bugs with specific models (under-screen fingerprint readers are a common one)

- As an actual consideration, the security model of Android is actually IMO miles ahead of Linux (assuming the mobile version copied the desktop in that regard). Apps are strongly sandboxed by default and there are plenty of tools to exert even more control, eg TrackerControl or Netguard to firewall them by domain, or Island/Insular to basically chroot them. On desktop OSes, including most Linux distro s, user apps have e.g. access to all of the user's files by default, which would be terrifying in the context of a phone.

(I imagine you already know most of that, I'm just laying out my reasoning for the same target audience as the OP's 'just install Termux' comment)