I've put a new SD card image for Raspberry Pi Plan 9 onto
the bell-labs.com repository, in /n/sources/contrib/miller/9pi.img.gz
I hope that mirrors like 9p.io can be updated soon to make
the new image available.
Apart from 3B+ support (including firmware files for the new
wifi chip), this update should make some improvement on all
Pi models: slightly faster usb and ethernet, corrections for
a few very old Plan 9 bugs flushed out by the Go test suite,
and some extra crypto support for better interoperability
with modern hosts using ssh and hget.