Sharing a site vs folder with external users (Guest accounts)

Sharing a whole site directly is less troublesome than sharing a single folder. To do this, first go to Site Settings > External Sharing and select Allow External Users (guests), then use the command Set-SPOSite -Identity <site URL> -SharingCapability ExternalUserSharingOnly to force it to take effect, and finally, don't forget to go to Azure AD to confirm that the guest account has access.