I use the free plan of appointment scheduling with Square and I really like what's offered at this level. You can set up your services, regular schedule, buffer times, exceptions, and so on. It integrates with my Google calendar and will block out time if I make a conflicting Google appointment. It sends reminders to attendees and also has the option to fake being a little busy, which could be helpful if you're just getting started and have wide open availability.
The overall tool is quite sophisticated so there are lots of aspects I don't need. And it doesn't let me customize the appointment confirmation, so even though I do online Zoom meetings, it insists on telling people that I'll be calling them on the phone number they gave. I don't think it offers group bookings (for example, 8 slots for a workshop), at least, not at the basic level.
But for free, I'm happy with it.
From what I can tell, it would be ideally suited to a business like a hair salon, with a real location and several staff. But it's fine for my needs, as a solopreneur doing online appointments.