I’ve student working on Glyphs 3 and the kerning does not export (the OTF file has no kern feature).
Something strange is going on, as opening the kerning window while in font view shows no kerning, but opening it in the glyph view shows the kerning pairs.
I opened the file manually and I see an
kerningRTL dictionary with the expected values. Oddly enough changing it to
kerning and re-opining and exporting the font seems to make kerning export.