seems to run fine on "macOS Sierra - 10.12.6"

miller: does it also run on "Mac OS X Lion - 10.7"?
(or even "OS X Snow Leopard - 10.6"?)

gffxyd
IOhannes

Nope - Wish 8.6.12 seems to depend on newer Mac features than are
on OSX 10.7.

But I'm OK with continuing to compile for 10.7 on my old machine and
make it available to people like me :)

Probably stick with Tk 8.6.10 or 11 for that build then.

Meanwhile, the jack mystery is still unsolved as far as I know (the
brew version somehow doesn't like newest jackd?)

As explained in previous emails, I don't use jack from Homebrew for my builds. I use the distribution from jack.org which is equivalent to the old JackOSX distribution:

You just need to download and run the installer on the build machine, which could also be automated via a script. People needing to use jack installed via Homebrew should build Pd themselves as the those libs doesn't seem to enable weak linking like the ones in the installer AFAICT.