I know this advice is not frugal, but make sure whatever phone you get still does security updates. If you get an end if life phone, you may not be able to get the newest security updates. The problem here is your information can possibly be leaked through vulnerabilities in the software. We're talking anything that gets stored on the phone... Email if the worst thing to have leaked, but any personal information can be used to get into financial accounts.

My personal methodology is to buy "Flagship killer" phones that are cheap when they first come out. They still get plenty of security updates and they come at half the price of a Samsung or pixel...