Can I configure that “include:_spf.google.com” is added to all new domain email dns records as I have my global relay configured to smtp-relay.gmail.com
I know I can change /usr/local/hestia/data/templates/dns/default.tpl but I assume this will overwritten upon updates? Is there a more permanent way to do this?
Yes, it will be overwritten during updates if you modify any existing template.
Just create a new template with a different name and it won’t be overwrtten in future updates. Just remember that you will need to select that template when adding a new dns domain.