Create your account through old.reddit.com; when it asks you for an email, simply press "next". And, if you need an e-mail provider for some other reason, protonmail.com doesn't ask you for your phone number.

That said do you really need a reddit account?

Protonmail?

Try Firefox relay. It can set you up with a randomly generated email address that will forward to your regular email.

tutanota didn't require a phone number, last I checked

Mailfence

I use m.kuku.lu, but if you plan to have more permanent account on there, like me, there's one problem it has. It NEVER invalidates old cookie tokens, even after a password change. This means if you get compromised or forget to logout on someone else's computer, there's nothing you can do about it.

Edit: Forget it, they recently added "Log out on all devices" button.

Edit 2: At the bottom of https://aquapal.net/ it also says they use solar power, if you care about that.

You can also just create an email alias for free with simple login (now run by proton, ie. Proton mail)

The last time I used the registry process, Outlook didn't.