Just recently, I received a grant to develop from scratch the single-person, self-hosted microblogging engine NLnet; #Seppo! being part of the fediverse but also offering a lean (atom) approach as well (inspired by https://mro.name/ShaarliGo).
I have some guiding principles in mind related to permacomputing, such as a static binary CGI, static page generation (for visitors who read), (mostly) immutable plain text data, 1-file copy install & upgrade, optional javascript, and various & small platforms (starting with like a Raspberry Pi Zero).
For me the best thing after basics is to get users and just keep solving their problems. Trading design and roadmaps for a steady stream of solutions to valuable problems is core to my favorite project management paradigm.
For testing, this was a neat idea but it fizzled out. I’d be interested to help resurrect it or to know of a replacement. I think many projects just setup other servers and do it manually or rely on bug reports.