As for LSB.. the use of USB for digital modes is by convention and shouldn't make a difference between QSO partners.
Neither question really calls for a change to FreeDV or anything from Flex. Good luck & enjoy operating!
Free DV flexradio ((wave form) is all usb all bands.
And the downloaded software from the author of freedv is 10meters-30meters usb and 40meters
-160meters is lsb. The standard conventions of usb-lsb.
This was my finding a while back and the flexradio (wave form) can not be changed from all usb to Lsb.
That's my understanding when I messed with it. So not compatible on 40 meters on down.
Understand this is not flexradio software.
If others use flexradio wave forms in usb that's works.
If others use the authors LSB modes that works but not crossed over on the side bands.