Why does AGH take so much fuggin memory?

[genki]

You can take a look here for AdGuard updates.

How to upgrade Adguard on the Flint, auto and manual?

Perhaps you used wrong architecture for Flint 2. You should use https://github.com/AdguardTeam/AdGuardHome/releases/download/v0.107.41/AdGuardHome_linux_arm64.tar.gz.