I haven't tried to attach files FROM the SD card, but I can verify that Beamberry 3 will open files FROM the SD card without needing some kind of desktop conversion. That's what made me buy the app. I hate that it needs to send files off fopr server side rendering, but I'll live with it as long as it dows what I need it to do (which it does so far - and i've tried with a variety of doc types).
Well, as soon as BeamBerry corrects the known issue they have, hopefully I'll be able to do the same. Glad you can open files from the SD card. At least I know the software is capable of performing that function.