Gsuite mandatory

Hi, using the wizard for a subdomain and needing to verify my domain for Google, I got keys for the domain itself which do not work for subdomain, then they say you must have a Gsuite. I must have missed the option without Gsuite. How should I proceed or is Gsuite really mandatory? Thanks (and as usual because Google is always changing them, your tutorial is outdated as the process as changed, or different from one user to another). Please help, thanks again for taking care of our questions.