Compile cinnamon from GIT on Ubuntu 19.10 (or later)
Basically, it's straightforward, but one can run into minor issue. First, you need all the prerequisites for building debian packages like dpkg-dev, C compilers, the full set of autotools and more. While building,
dpkg-buildpackage is verbose enough to indicate missing dependencies. Should that happen,
apt install them and restart the build process.
Follow them step-by-step.