I have been messing around with my Mac Mini 2009 that I would like to setup as a standalone Ubuntu box. However, after several attempts the main disk is now fully wiped and I can not re-install osX anymore. I hence downloaded the Mountain Lion dmg and trying to build a USB installer stick.
What I previously did was to install rEFInd and Ubuntu 20.04 where I entirely formatted the whole disk to xfs (or so, don't remember). I installed the 3rd party wifi driver that worked but the NVidia driver failed. After a reboot, linux does not complete the boot. I see a Ubuntu spinwheel screen but then it does not load unity. Switching into text only terminal with ATL + F2 fails too so no way to communicate to the system, needs. a re-install. But how? My guess is a OSX USB installer. I have no OSX DVD here (Those minis have a disk drive, yes).
Long story short, how can I create a bootable USB stick out of the downloaded Mountain Lion DMG? I tried with
dmg2iso but etcher tells me that there is no bootable partition on the iso.
ADD ON: I have a working Big Sur MBP sitting here where I am writing from. I can create a bootable USB there with Etcher or in a Debian VM I have here...