Hi Eric,
indeed from FF 57 Vimperator doesn't work at all. Mozilla underwent very major changes in FF api, which they announced months or years ago. It's both too radical for Vimperator to follow and too limiting, some things are not possible any more (working in Addons page, the colon operator,…).
The developers are in relation wih Mozilla to improve those limitations, but in the meantime, we can either use an older FF (
FF ESR, Iceweasel,…), try another addon (
Vimium-ff is ok) or another browser (some like
Qutebrowser for its minimalism).
in-depth discussion and more solutions:
https://github.com/vimperator/vimperator-labs/issues/705#issuecomment-335908307