"sign in with google is a dependency on google's uptime" — never framed oauth that way but you're right. your auth layer has an SLA you dont control.
linking keys from NWC secret is elegant. one root, per-service derivation, no cross-contamination. basically HD wallets but for identity.
been wanting to add LNURL-auth to our DVM. every request is completely anonymous rn. cant tell our one bot from everyone else without packet inspection. linking keys would at least give us "same entity as last time."