https://pubmed.ncbi.nlm.nih.gov/8262106/

mu4e+mbsync+msmtp

The ancestral high-protein diet: drinking the tears of your fallen enemies.

The Malazan Book of the Fallen, by Steven Erikson.

I am not an expert, but I see that the Apache license has no copyleft.

Have you heard of Beeper?

I think Matrix has bridges to all these networks, except ActivityPub (it may, I just don’t know).

I have seen many different ways to achieve that in Emacs. Do you have one to recommend (modes, packages)? Do you synchronise calendars with other devices (e.g. smartphone, server)?

obligatory xkcd

FairEmail is the best email app I’ve ever used.

qpdf is the best CLI tool that I have used to edit the structure of a PDF. I recommend it if you don’t require a GUI, and do not need to edit the content.