[Csnd] recent build - install FLTK libstk0 issue

On a fresh Ubuntu machine, I am looking at the install and build instructions here,

If FLTK is being deprecated, can I simply leave that out from the apt install?
I'm not sure about the libstk0-dev I've turned source code on for the repositary.

$ sudo apt-get install cmake libsndfile1-dev libasound2-dev libjack-dev portaudio19-dev
libportmidi-dev libpulse-dev swig liblua5.1-0-dev default-jdk libfltk1.1-dev
libfluidsynth-dev liblo-dev fluid ladspa-sdk libpng-dev dssi-dev libstk0-dev libgmm++-dev
bison flex libportsmf-dev libeigen3-dev libcunit1-dev gettext libsamplerate0-dev
[sudo] password for user:

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done

Package libstk0-dev is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Unable to locate package libfltk1.1-dev
E: Couldn't find any package by glob 'libfltk1.1-dev'
E: Couldn't find any package by regex 'libfltk1.1-dev'
E: Package 'libstk0-dev' has no installation candidate

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