I am afraid having to tell you, using typical unmodified Android looks like not being the proper OS for your expectations on data security.
Maybe you feel like reading through a posting of mine in the past, specifically following the link about security updates (sorry only in German).
So you may be so kind and enlighten all of us with your positive experiences from your past with “other” smartphone manufacturers using Android and delivering monthly security updates for years for all of their models just as Fairphone could manage the last 5 years?
Naming one specific model out of billions that receives regular OS upgrades & security updates would be fully sufficient.
If still being available for purchase many security concerned users will surely put energy into getting their fingers on it.
Many thanks in advance.