I've created a nostr:npub155m2k8ml8sqn8w4dhh689vdv0t2twa8dgvkpnzfggxf4wfughjsq2cdcvg plugin for aMember Pro. It allows you to accept #bitcoin for recurring membership subscriptions.

It's available free on my GitHub:

https://github.com/robwoodgate/am-btcpay