Outlook Add-In - Launch event and more for Exchange On-Prem

Question

We are required to upgrade all of our Office Add-ins from VSTO to Web Add-in client plugins to support Office 2019+
We are developing an Outlook web add-in for an organization using Exchange Server 2019 (15.2.986.5) on-prem
The client version is Outlook 2019 on Windows 10/ Windows Server 2019
We encountered several problems:

1. LaunchEvent, by https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/autolaunch?tabs=xmlmanifest#configure-the-manifest
   When I try to sideload manifest, I get this message:
   The API version (1.10) required by this app isn't supported by the Exchange Server version (15.2.986.5) that you're connecting to
   But by the requirement set version 1.10 is valid for outlook 2016 and later
   but not supported for outlook in the browser.
   How I can add an add-in to outlook 2019?
2. Outlook add-in isn't available from the shared calendar.
3. How to know, who is the appointment organizer in the shared calendar - Office.context.mailbox.item.organizer is undefined
4. itemID that saved in exchange server is undefined - Office.context.mailbox.item.itemId is undefine

Kind regards,
Braindy

Answer 1

So called "modern" add-ins are working bad with desktop Outlook. Use the COM add-in as bedore.