Ask HN: Registrar, email provider, and recovery email contact info best practice

I often read on HN that paying for a custom domain is recommended for email, one of the reasons being that you can switch email providers at any time, or even host your own.

One thing I never see mentioned as part of this recommendation is how to handle contact information for your domain registrar, your recovery email with your chosen email provider, your DNS provider, etc.

For those that do use a custom domain, what do use as your email for these services? For instance, I use G Suite currently for my custom domain email provider and my recovery email is a free gmail account. Is it better to have a second custom domain email be the recovery email?

What about for your domain registrar? It seems like a circular dependency to use your custom domain email as your email address for the domain you are registering. Do you use a free email account for that as well, or do you use a second custom domain? If using a second custom domain address, obviously for the first one you need some kind of freely provided email first.

Really, I'm just trying to figure out, if I switch to using a custom domain address as my primary email, what email is best to use to sign up for the core services that provide access to that custom domain (registrar, DNS, email provider), and what is the best recovery email to use (custom or freely provided)?

Just want to avoid any circular conundrums or potential account lockouts down the road. Thanks for reading, and for any help you can provide!