Hi Dan, thank you for the quick turnaround!
As far as I’ve been able to gather from these docs and this forum, the Lock page does not work on certain browsers and it is the Universal Login page that Auth0 is recommending.
My central problem: these days iOS Safari, among other browsers, has third party cookies disabled by default. This causes the Lock page to fail unless you also use a custom domain. Unfortunately, the custom domain is only available to paid plans, and since we are bootstrapping our startup, we can’t afford to pay $745/month right off the bat (we make use the Management API).