libosmo-sigtran doesn't reject M3UA with "M3UA Network Appearance"
libosmo-sigtran has no support for "M3UA Network Appearance". Right now this means that peers using this optional M3UA IE will be able to send us such messages, the IE will be ignored and answers will be sent without that IE present (which the recipient likely cannot process properly).
I think the clean way would be to print error messages if we ever receive such messages, and send related error messages back to the sender. This way it becomes obvious in both log files and protocol traces that there is an incompatible feature at play.