I have a couple tracker files that I would like to export to FLAC, but I haven't been able to open them. I can't seem to find a program that supports exporting them either.
Neither of those two formats are easily implementable in OpenMPT, hence it does not support them. I wonder how much you invested into your search though because a simple web search for "ahx file" or "a2m file" would give you plenty of options - AdlibTracker 2 (http://www.adlibtracker.net/) being the obvious choice for A2M files (as that is its native format), and for AHX you can use HivelyTracker (http://www.hivelytracker.co.uk/).
I tried HivelyTracker, but I couldn't find an option to export the file to a normal format. Was I just missing the option somewhere? Will check out AdlibTracker 2.
Then you may want to look at XMPlay and its AHX/HVL input plugin. There's also and AdPlug plugin which should support A2M but I have no idea how accurate its A2M support is.
I used the record function of AdlibTracker 2 and that worked. XMPlay failed to export as FLAC but WAV worked fine. Converted both to 16/44.1 FLAC and all seems to be good, thanks.
While XMPlay has a few presets for various encoders, it does not actually ship with those encoders, so you either need to place flac.exe in the XMPlay folder or point it to another location where it can find that.