Sure, but what if that computer doesn't have wireguard installed. I don't see any other way except exposing the service to the public.

How do you access those services from a public network? Say, you want to access something while working from your office or a friend's computer.

Try this: bore

For domain names, you can go with any reverse proxy like nginx proxy manager or caddy or anything else you like.

Are there any third party services that don't require phone numbers for sign-ups?