I tried to avoid retyping ssh passphrase for git. Turns out there's no one way to it.
Not sure why keychain vs ssh-ident counts as opinion-based.
Also, that question was asked for a full linux system where distribution-specific things like gnome-keyring was suggested. I am looking for a generic solution for WSL2.
keychain and ssh-ident seems like 2 options that strike balance between security and convenience(based on https://unix.stackexchange.com/a/90869/306145).