devuan alpha and Xfce wouldn't play nicely on my old 6,1 24" iMac.
ctwm worked well but the normal people in the house were not at all happy.
Perhaps moving on to devuan Ceres would be good? All the latest stuff
and Xfce is bound to work!
No.
Worse off if anything. Many heavy-duty changes as debian is further
polluted by systemd and also morphed into becoming devuan.
Ah well, it's not called 'unstable' for nothing!

In my mission to avoid systemd I even tried OpenBSD and NetBSD, I
couldn't make sound work on either of them. FreeBSD fails to even
install because of the peculiar 32bit EFI that my early Intel iMac has.

With a heavy heart I installed debian jessie, systemd and all.
Everything including Xfce works, it is debian after all so of course it
works, but the dependencies are horrific.
And, should anybody need to know how to install on an aged iMac, you
have start with debian 6 squeeze because that is the latest version that
will boot from CD.
Do a minimal install without X11 because then you need to upgrade to
debian 7 wheezy, and then do the same again to get to debian 8 jessie.

DaveT