Cannot add a meeting from a channel in Teams in the own calendar, where mailbox in on prem and there is a Hybrid environment. Creating a new meeting in Teams and in calendar on-premises is working. What is the reason for that? Can somebody test it in a hybrid environment?
I just tested it in a hybrid setup with the mailbox hosted on-premises and it works without any issues.
When you create a channel meeting, all members receive a meeting invite in their personal inbox. When a user accepts that invite, the meeting is added to the personal calendar. You can add additional recipients to the meeting invite, but this not necessary for meetings targeted at team members only.
When you create a channel meeting, and the members do not receive the invite, then you are facing an email routing issue. Verify the mail flow configuration of your hybrid setup with Exchange Online.
Microsoft Teams sends the invite using the Teams' (Microsoft 365 group) email address. Microsoft 365 configures this email address when you create a new M365 group. The interesting part is, that Microsoft 365 uses the tenant domain that is configured as the "Standard" domain. Which might be still the tenant domain itself: tenantname.onmicrosoft.com. You can verify this very easily using the Exchange Online Admin Center. After checking for the Teams' email address check your mail flow configuration from Exchange Online to your on-premises Exchange organization. Maybe an on-premises SMTP device rejects the inbound email.