The motherboard can be cleaned with a generous amount of isopropyl alcohol. It cleans slightly corroded areas, displaces water, is not a good conductor of electricity and evaporates easily.

The FSF has clear guidelines and follows them rigorously, nothing else. It’s good that they don’t make exceptions. Any problem with microcode or other proprietary drivers starts with the fact that they are not free. Making exceptions would partially solve the problem, but the situation would not change significantly, and the FSF would then be violating its own principles.

The FSF’s job in this regard is to try to open debate about the problems of not having free security patches and, in any case, to try to uncover hidden vulnerabilities in proprietary tools and facilitate the creation of free tools that solve the problems.

I was going to recommend Tox, but I don’t think there have been any iPhone clients with up-to-date development for years.

You can also try Jami.

https://jami.net/

The most reasonable thing to do is to cite the original publication and its author.

Literally.