That's Not How a SIM Swap Attack Works

Article is leaving out Number Lock (not to be confused with a SIM PIN). Many providers now have the option to lock the SIM to a phone number. This does not stop the provider from having bribed employees but it is better than nothing and limits bribed employees to your provider vs all the providers.

For email addresses use a canary email for each and every company. Canaries are really just aliases. Don't put their name in the alias. Some mail providers will allow you to create aliases using some of their domains and will also allow aliases for your own domains you point to them. Store the alias in your password database such as KeypassXC.

In terms of leaking ones number avoid any business that requires a number or use a throw-away VoIP number. If they reject the VoIP number consider that a red flag and avoid that business at all costs unless they are physically in short driving distance and you know where all the employees sit and you have a business relationship and contract with them meaning if you have a complaint they and their management have to listen to you, your lawyers and bodyguards in person.