It's not a great option. My "old" phone that I use to install junk apps (e.g. I buy some hardware that requires an app to set up) and which mostly sits in a drawer is a 2nd gen iphone SE, and it's getting to the point where I'm going to be forced to replace it, because the OS hasn't been upgraded in a while (it errors) and some apps won't install on it now.
12 mini is pretty old. I have considered going to a 13 mini, but I sort of hate the idea of spending money on a phone that is already well on the path to unsupported. Then again, the compact options for grapheneos are limited to old stuff too. Sigh.
