In my book, it’s essential. I’ll never use email without a custom domain, because otherwise you’re completely beholden to whatever email provider you signed up with. I’ve migrated providers many times (probably 6 or 7 now) and never had to change my email address. I have:

• Work domain
• Personal domains (one for myself and family, one for my band, a few others)
• Domain for aliases / signups

I’m currently with Fastmail which can generate aliases on the fly with your custom domain of choice, and they allow a ridiculous number of domains (100?) on your account.

Do you use random strings before the @ sign? Or do you use it like [email protected]?

I use random strings when I sign up for an online service, but the emails I actually give to people are firstname@domain

Because I’m considering using this as a catch-all address, doesn’t this mean that anyone who wants (and knows the domain) and send spam on any random string before the @? Are you worried about this, and are there any counters to this?

The only counter I know of is to create specific aliases rather than use a wildcard. However, in practice, I only very rarely get emails at my wildcard domain (one a year, if even)

As far as I’ve understood the main benefit of using my own domain for email, is that it will make it a lot easier to change providers in the future, as I can just change the nameservers so traffic is directed elsewhere - correct?

Exactly, so there’s zero downtime and you don’t have to change your email everywhere. The only annoyances I’ve run into are migrating away from Proton because it’s encrypted and a huge PITA to get out of, and having to redo my automation filters when switching providers.