When I use “Filter > Glyph as Image” any part of the glyph below the baseline gets dropped. Fir example, here’s what a g looks like exported from IBM Plex Mono. It happens for pdf, png, or svg export. Note that the image is exported at the correct size. The image is offset vertically down by the height of the baseline (with equivalent margin on the top).
It’s not the cubic / quadratic issue as it happens whether I convert to cubic or not. (However, if I don’t convert, the svg of this glyph is mangled as is a known issue.)
I can workaround it by setting the descender depth to 0 and moving all the glyphs up by a corresponding amount. (Btw, would be really nice to have bulk png export.)