Given that most old Android phones stop receiving security updates after only a couple years from purchase, you should probably not do anything that involves connecting them to your local network.
What would you suggest these days, my phone is certainly out of date security wise and I need an upgrade. What have you yourself purchased?
I've been commenting so much on this that it probably looks like astroturfing, but I know how deep of an itch this is to scratch, so:
GrapheneOS.org
And if you don't have or can't afford a Pixel, you can check if your device is supported by my https://divestos.org project. Tested booting on 70+ devices with automated kernel CVE patching and monthly security updates.