This article:
https://listoffreeware.com/free-open-source-grammarly-alternative-services/
… refers to some tools for language improvement when authoring text.
LanguageTool, for example, has a Firefox add-on I just installed that has immediately started working in this very box I presently am typing into
Therefore, presumably, it must be using WebExtensions as the API
Better still, LanguageTool is open source.
Anyone aware if there are any such Grammarly-like alternative add-ons currently working in Thunderbird? Or if there would be major barriers to porting this, or similar, add-ons to MailExtensions?