Since my last update, I changed my mind on the release plans for Clippings and Clippings for Thunderbird. There will be a new version released later this year to coincide with the next Firefox ESR version. I felt that it was better to spread out the changes to Clippings over two release cycles so that users don't have to wait too long to receive improvements and bug fixes.
With that, I've started working on improvements to the back end of Clippings, with more work planned over the next few months. The scope of the back end improvements is limited to refactoring the background script; migration to Manifest V3 is deferred to the next release.
I'm also planning on starting work on a new minor version of Read Next, which will come with small improvements. More on this will be announced soon.