Forms built within a team are automatically available to members of your team. Forms can also be shared with people outside of your organisation without any additional licensing. The external users can be a personal Microsoft account (e.g. firstname.lastname@example.org) or Work/School account (e.g. email@example.com) or completely anonymous.
To share your forms externally you can use the following steps or generate a public link:
Invite the external user into your team using Microsoft Teams as shown below
Once the external user accepted your invitation to the team they can easily access your forms by following the link in the email sent by Microsoft or by logging into Microsoft Teams, selecting your organisation and navigating to the Team Forms channel app. Alternatively, your external user may access Team Forms in the browser using the multi-account feature.