sorry if it is trivial, but
tar xvf flair-3.1-4.tgz
cd flair-3.1
make
and then
make install
seems to work
if I try the same with flai-geoviewer it fail in the first make
-Wwrite-strings -Wshadow -pipe -pthread -fwrapv -fstack-protector -fpic -fno-strict-aliasing -I. -I… -I/usr/include/tcl8.6
geometryobject.cc:12:10: fatal error: Python.h: No such file or directory
#include <Python.h>
^~~~~~~~~~
compilation terminated.
makefile:312: recipe for target ‘geometryobject.o’ failed
make: *** [geometryobject.o] Error 1
but
which python
/usr/bin/python
python --version
Python 2.7.17