Thunderbird Lightning Exchange Calendar
Howto: Exchange Calendar in Thunderbird Lightning
Attention: This method works fine for pulling events from Exchange calendar but
has issues when pushing into Exchange.
e.g. changing status to Accepted or Declined does not work.
(for me workaround is to accept or decline on my cell phone)
There is another (paid) option. See discussion on confluence page: https://confluence.oraclecorp.com/confluence/display/cel/Configure+Thunderbird+Calendar+for+Exchange
Thunderbird - Lightning - Calendar
You need following Add-Ons:
Install them and restart Thunderbird
Check in Add-Ons if enabled:

Open TbSync (Tools -> Synchronization Settings (TbSync)) -> on Linux (in Edit menu)
Account Actions -> Add new account -> Exchange ActiveSync

Select Microsoft Office 365 and provide Account Name (any name) and your SSO login
as below:

After clicking Add Account you will be redirected to SSO login page. Login
with your SSO credentials

After successful login you can see your account:
Enable and synchronize this account needs to be checked and under Available
resources select what needs to be synchronized (Calendar). After that click on
Synchronize now
In this window you can set Periodic synchronization -> this is the number of
minutes every which the synchronization will take place.

In the above example every 5 minutes calendar will be refreshed.
To force refresh of calendar (and not wait for the number of minutes for periodical refresh) you can click in the bottom right corner as below:

In the opened window click on Synchronize now as shown before.
If everything went fine you should see in Calendar tab entries from Exchange calendar:
