Thanks for doing the work of comparing Tidycal and Calendly for me! I was just thinking about which of these platforms I wanted to use for my client workflows. I may end up going with the Google Calendar appointment scheduler until I finish reworking my workflows.
To piggyback off of what you wrote in your FAQ section, the Google version of Calendly would be the appointment scheduler in Google Calendar. I'd assume that the readers of this article may be entrepreneurs or business owners of some sort and may already have a Google Workspace account.
Per Google, appointment scheduling allows you to manage your availability and let clients, partners, friends or family book time with you directly within Google Calendar via a personal booking page. If you use Calendar with a personal account, you can create a single booking page and accept unlimited appointments at no charge. More premium features require Google Workspace or Google One subscriptions.