Just a FYI - not sure if anyone uses Thunderbird, but for reference they
have released another half baked version which attempts to break lots of
your extensions if you try and upgrade.

This has a decent summary of the issues:

https://www.mail-archive.com/dl-ticket-service@thregr.org/msg00459.html

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"TB 60 decided to jump on the new FF engine, and as Firefox with the 60
release, the following happened:

- TB 60 doesn't have the WebExtension APIs required yet to develop
FileLink extensions.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1481052 TB 63
"should" be the first TB version that includes the required API. At
the time, the API is still being discussed.

- Despite knowing several extensions won't work with TB 60, they still
decided to disable "Legacy extensions" by default. Note that,
contrarily to Firefox, TB extensions won't have *anything* in common
with other browsers or clients, so there's no rush for "WebExtension"
compatibility here.

- TB also deliberately changed several APIs with TB 60, which they could
have avoided. This broke existing "legacy" extensions exactly at the
worst possible moment.

- Cherry on top, TB also removed the installation of the xpcom SDK,
which caused Debian to drop most of the utilities *needed* to
fix/rebuild the extensions.

Just like FF 60, I'm actually mad at how the transition was handled.
TB is clearly understaffed, but there's no excuse for such a poor
release handling. TB 60-62 will require a specific extension just for
the transition period, and that code will have to be trashed again for
TB 63."

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Unfortunately you get banned/blocked/censored by Mozilla if you try and
voice any form of dissenting opinion (I'm seriously unpopular over
there....!)

Shame on Mozilla.

They should have just released it fully rather than this halfway house.

Death by slow strangulation.