User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36

Steps to reproduce:

We use google calendar in our organization.

1. Have someone (else) create a meeting
2. Have them cancel the meeting (google calendar) along with a note (Reason)
3. View the cancelation email in thunderbird

Actual results:

Thunderbird shows the cancelation email. THe subject of the email is

Canceled event with note: Weekly S/W Sync @ Fri Sep 6, 2019 9am - 10am (IST) (bhakta@XXXX")

However, the note is not displayed anywhere.

Expected results:

Thunderbird should display the note that was added when the meeting was canceled.

The same meeting, when viewed in gmail, show the cancelation reason correctly. I have attached screenshots of gmail and thunderbird.

Note: If I click on "More" and "View source", I can find the note buried inside. You will find the "Many meetings this week + No clear agenda" string below.

<snip>

px Solid #fcc;background:#fcc;color:#222;font-weight:nor=
mal"><strong>This event has been canceled and removed from your calendar wi=
th this note:</strong><br>"Many meetings this week + No clear agenda."</h4>=
<div style=3D"padding:2px"><span itemprop=3D"publisher"

</snip>

Confirming as I've seen this as well as others.

IIRC this is because that note is not in the event part of the mail, it's in the plain text (or maybe html), and for multipart/alternative only one part is supposed to be shown...

The attendees list is also coming from the multipart/alternative. That seems to be showing up right? I have attached the "View source" output

multipart/alternative here has text/plain, text/html, text/calendar along side of one another. Then also an application/ics as attachment.
This is bug 1406868.