I have oi_151a7 and installed from sfe fuse-ext, libfuse and e2fsprogs. Mount e.g.
# mount -F ext2fs /dev/dsk/c4t0d0p1 /mnt
returns
"mount: Operation not applicable to FSType ext2fs"
and
$ fuse-ext2 /dev/dsk/c4t0d0p1 ~/tmp/a/
does not output anything but the filesystem seems not to be mounted.
What packages and commands do I need to mount an ext2 filesystem?
(Or would it be easier to mount a OpenBSD ffs?)
Indeed, I guess Corona688 confused OpenIndiana with a Gnu/Linux distribution. /proc/filesystem and mount -t are both Linux specific.
If you properly installed these packages and they still don't, chances are they are no more compatible with the current illumos kernel. There is work in progress to include ext2 support on Illumos but it is not completed: