Is there any open-source way to create OpenType variable fonts yet?

FontForge isn't there yet: https://github.com/fontforge/fontforge/issues/2882.

Is anyone aware of a free and open-source solution for creating OpenType VFs? And yes, I'm well aware of the commercial solutions; I'm not interested in them. Right now, I am aware that FF has some MM support (not OT1.8) and METAFONT can create variable fonts, of course, but again, not of the OpenType variety.

[Addendum: I guess it is possible in some way to do, by creating a file manually, and the using fontmake, but this is extremely painful and not practical. But maybe that is the way to go.]