Old phone? I’m still running a Mi A1 as my daily. I’m on LineageOS 19.1. There have been rumblings of Lineage 20 coming to it, but the Dev community has largely dropped off.
I’d check if there are any local high-schools or support services that are looking to get phones intot he hands of underprivileged teens/adults. A Mi A3 is likely still better than the low end Samsung garbage, or even an old iPhone (below X).
Better to have it be reused than become a paperweight in a cupboard.