I was struggling to get quicklook previews of markdown documents in macOS Catalina to work due to the new enhanced security checking. The various open source and self-install solutions out there all failed, even after following all kinds of convoluted procedures.
The solution was PreviewMarkdown which installs via the app store and satisfies all of Apple's new security requirements. It costs $1 which is worth the no-hassle install.
SFLphone is an open-source softphone for VOIP, it supports the standards like SIP and is completely skinnable. It’s in early stages right now and has only been compiled on Linux, but support for other platforms is planned. It’ll be interesting to watch how people will tweak it and integrate it with existing applications.
Mac users: the first public beta of Omniweb 5 is out and first signs are good. Lots of cool stuff including workspaces (fantastic), rss support, shared bookmarks, popup trap, loads of useful little extras for web developers, and much more… The version of webcore used is a bit behind Safari feature-wise, but that’s a small detail compared to all the rest.