What can be run on the early 10.6 betas on PPC that can't be run on 10.5?
Well, I think my point should be fairly uncontroversial in principle, but pinpointing specific case right now is not easy for two reasons: a) I work predominantly on 10.6 PPC and 10.6.8 Rosetta, my only interest with 10.5.8 was related to ppc64, and that is largely broken, so to discover what software builds on 10.6 PPC but not on 10.5.8 I need to try building substantial number of ports – and for that I need identical compiler, which means I need gcc12 on 10.5.8, and that requires some time; b) since I had no such objective, I did not make a record of what has been shown to be broken on 10.5.8.
One thing I am quite sure about –
Ruby 31 built on 10.6 PPC and failed on 10.5.8 (does not in itself mean it cannot be fixed for 10.5.8, but what worked on 10.6 failed on 10.5).
Another likely case is
libsdl2 – I am quite sure a newer version will be supported on 10.6.
Again, as I recall,
i2pd is broken on 10.5.8 (at least was few months ago), but built on 10.6 (still needs fixes, but at least it builds).
I would assume
folly and friends may not build on 10.5.8 – that I will test, but again, gonna take time: need to fix Boost first.
UPD. Fixed Ruby and Folly & friends for Leopard.