Installing Tk On Linux

Pretty much all Linux distributions have Tcl/Tk packages available via their package managers, e.g., apt. Usually there are a variety of packages, providing libraries, command-line tools, development options if you're building extensions, and many more. On Ubuntu and many other distributions, apt install tk8.6 should be enough.

By the way, you need to install pkg-config to compile the tcl/tk crates.