Hi,
The only supported connection type for mobile interface on RUTX and TRB devices is QMI.
Separate PPP type will not be developed as QMI should work with most operators out there at the current moment.
If you're having struggles to make RUTX or TRB work with some kind of operator, you must ask if operator is able to include QMI connection type into their infrastructure.
Unfortunately, right now, there are no plans to include PPP as a connection type into these products.
EB