Teams not available in Outlook (Mac)

beanbagdan The free Teams personal version doesn't have the same integrations with Outlook as the 'Work or School' version, you can book meetings, but you would need to do it from within Teams,

Create a meeting in Teams for personal and small business use (microsoft.com)

I would suggest in your situation I would be wanting to book meetings using the accounts provided by each customer, that way the appointment, meeting etc stays within their tenant and control. I would use three browser profiles to log into Teams for each client, and then book meeting from the calendar there. By all means have all these accounts sync back to Outlook for Mac so you can see them all together.