downloaded a binary for agate from
https://github.com/mbrubeck/agate/releases/tag/v3.1.0
and stuck it on my PATH
then cd somewhere/with/an index.gmi in it,
agate --hostname localhost --content . --addr 127.0.0.1:1965
visit localhost with lagrange and up pops the content of index.gmi.
virtually painless!
/gemlog/