Modern browsers at 97% according What can I use supports woff2.
As a fallback, we offer TTF.
A more careful user-agent analysis could be done in Lua, to serve
EOT/SVG/WOFF/WOFF2/TTF but now woff2 is supported everywhere,
the point is somewhat moot.
According the user-agent header, the visitor is served
<font>.css-with-woff2 or <font>.css-with-ttf.
Ref T1881.