Thanks, let's dive in, shall we? What issue were you experiencing with the Pi4? I'm asking because there is a common misunderstanding that the entire UTXO set needs to fit into RAM, but that is not the case. The UTXO set is mostly stopped on disk. You only need a couple gigs of RAM for Bitcoin Core to run decently, although more is certainly helpful. UTXO set growth means slower IBD and generally more disk reads during validation, but it's a graceful degradation, not a cliff.