One of the benefits of ticketing your own shows using a service such as Eventbrite is that (subject to GDPR and other permissions) you can acquire fan email addresses as they order their tickets.  If a venue or another promoter tickets the show you won’t have access to those emails which means you’re missing out. Here’s one way of circumnavigating that.

In the Facebook event (or elsewhere on social media) offer people attending the show a freebie (badge/button, sticker or copy of that EP that you still have hundreds of left in your garage!).  To claim their free gift all they need to do is email you a proof of ticket purchase (such an order confirmation number).

By them emailing you now have their email address, reply back with how they can claim their gift at the merch stall and state if they’ve no objection they’ll be added to your band newsletter so they can be kept up to date with future happenings. Don’t forget to include your privacy policy in the footer of your band email.