the mozilla browser seamonkey
is a self contained tarball
there is NO needed extra software
I have been using it for YEARS!!!!
and there also is no such thing as "GTK2 format"
the CURRENT stable mozilla browser is here
https://ftp.mozilla.org/pub/mozilla....releases/2.33/
all that gtk part in the name on the download link is that it uses the older gtk2 engine
( The Gimp ToolKit 2 -- gtk2 )
and not the gtk3 version that gnome3 uses
the 64 bit version that uses the 64 bit plugins ( NOT!!!! the 32 bit ones in /usr/lib/? )
https://ftp.mozilla.org/pub/mozilla..../2.33/contrib/