Contact the add on author. They are responsible for keeping their software up to date

Is this a Mozilla policy? To not try to maintain backwards compatability for the arm of addon authors? Have they no concerns that a large number of Mozilla's customers rely upon such addons? It seems arrogant and high-handed to put all the blame on developers for not constantly playing catchup.

Time to explore more customer orientated software methinks.

Thunderbird is the software program. The developers make updates as needed. Approved add on authors get plenty of notice of the upcoming changes. Some add on authors just stop development because even after asking for a small donation to use their software people just use it for free and then complain when it stops working. Do you get this upset when Microsoft updates their software and a 3rd party software does not keep up. You obviously do not understand how software development works.

There are no Mozilla customers. Claiming to be a customer implies you paid for something. Thunderbird is no longer developed by Mozilla. The Thunderbird Council has taken it over to keep it going.

Version 5.35 of S3 Translator works here in TB 52.7.

https://addons.mozilla.org/en-US/firefox/addon/s3google-translator/versions/

Drag the Download Anyway link and drop it onto Tools/Add-ons/Extensions in TB to install.

https://support.mozilla.org/en-US/kb/installing-addon-thunderbird