These do not work. They are not going to be supported (class 1 faxing is a mess, and the timing is extremely critical—nearly impossible in a unix environment—read the comments to the FlexFax/Hylafax package for details).
Update: some very preliminary support is in the code now. It’s known
to be incomplete in a large number of places. If you feel adventurous,
compile mgetty with -DCLASS1, and try it – but I will NOT give
beginner-level support here. If it doesn’t work, send the log file of
a problematic call, unmodified and complete, at debug level 6.