The best practice is to abandon locked down Android phones and switch to GNU/Linux phones (Librem 5 and Pinephone).
It was mid-spec a half decade ago, and hasn't changed since. You're really paying a lot for that old hardware. This won't help adoption.
We're at a point where any successful mobile OS will at least need to support running Android apps, preferably directly from the Play Store. I suspect this is one of the reasons Microsoft is adding Android support to Windows 11.
I like the idea of an entirely FOSS phone, but sadly that ship sailed years ago.
You need separated devices, and do the anonymous stuff in the most private one.
It is the same principle as having separate machines for work and personal stuff.
Yes, it is "impractical". That's unavoidable. Let's keep the conversation on what can be done, not some theoretical perfect device no one will ever make.
Fortunately, for normal computers it's not necessary, because we have Qubes OS for that: https://qubes-os.org
Worse the radios don't support everything my carrier does. 5g is a must where I live as 4g is being skipped in remote locations that are finally being upgraded from 2g.