Solved the autotools build system issue that I had, see here for details:
And I managed to run my app using:
flatpak run --socket=session-bus --nosocket=fallback-x11 --socket=x11 org.flatpak.atomes
The ‘–socket=session-bus’ correct the DBus error, while ‘x11’ related options correct a GTK display error, so now the flatpak seems to run fine, not sure that this way of doing is appropriate,
any advise would be appreciated.