TidyCal

When purchased, Tidycal was a no brainer : configure, share a link and start receiving new meeting invites in your inbox.
Only Google and Office365 were supported : that was okay for the price. I use Zimbra for GDPR reasons, but I could setup a dedicated gmail agenda to share my availability with tidycal.

One day, Tidycal team decided to suppress sending meeting appointment confirmation but just a useless "tada mail: you got a new booking". With no plan to restore this basic feature, and no real explaination on why they removed it. So, from now, either I stop using my paid Tidycal, or I need to manually copy the appointment details into my Zimbra calendar (instead of just clicking on "accept" or "add to my agenda").

So, if you're okay (and can) with sharing your whole gmail or Office365 agenda with tidycal (wich may be a security concern), this tool still has a good feature/price ratio. But beware that any feature you value may disappear at any time.

And otherwise,