What's the best guide/doc/walkthrough for deploying cashu from scratch in this manner when I already have a lightning node on a personal Ubuntu server?
Srill too experimental, Cashu gateways were invented around 12 hours ago. If you want to set one up, join our Telegram or discord to find like-minded crazy people: https://t.me/CashuBTC
I'd use your gateway.
I'd use your gateway.