I am not sure if it covers everything, so feedback is more than welcome. @mkasimd maybe you can take a look?
Note that I have also enabled BIMI, Gravatars, Libravatars and favicons for the Play store version again.
The short term goal is to release a Play store test version (and associated GitHub version) and to get the update approved. I will think about the next steps after this has been accomplished. Given the huge number of supportive messages I received (much appreciated!) the project will be continued in some form in any case.