Umbrel + LND + btcPayServer + kraken plugin. Umbrel stays at home. You can have an unlimited amount of Point of Sale terminal apps on staff phones to take payments which connect back to the Umbrel. They can take a payment in btc and it will immediately be forwarded to kraken and sold. Can withdra...

Good question, and for a merchant who doesn't care about crypto, the hard part is usually the cash-out, not the wallet. A self-custody phone wallet keeps the keys with the seller, but they will still need an exchange that pays out in AUD to turn coins into dollars, so check that route before recomme...