But for now I was thinking of trying linux on the A4000T which has a cyberstorm (68040 on 40Mhz) and the picasso2 and 80 Mb on board.)
Surely this is powerful enough to try linux?
Yes. Linux runs on it for sure, but don't expect ultrafast experience with X.
But what to install? Debian version number?
Debian stable (woody) is a good start.
Stable has the most complete
installation manual. Later I'd recommend you upgrade to
Debian testing (sarge) (it's just matter of changing apt sources.list lines and apt-get update && apt-get dist-upgrade).
It's also possible to install sarge directly, but this is less documented.
Does it contain the picasso driver?
Yes. Linux (the kernel) includes cirrusfb driver:
Chip families supported:
SD64
Piccolo
Picasso
Spectrum
Alpine (GD-543x/4x)
Picasso4 (GD-5446)
GD-5480
Laguna (GD-546x)
Bus's supported:
PCI
Zorro
Architectures supported:
i386
Alpha
PPC (Motorola Powerstack)
m68k (Amiga)
Also,
Debian 3.0 (woody) for m68k -page could prove useful (yeah, kas1e posted this link already).