Help Deleted Mac Partition!

I installed Ubuntu Bungie to my external drive of my late 2013 iMac. When I did I deleted the Mac partition, which included the Mac bootloader and the Mac bios so I cannot access the Mac recovery tool to reinstall Mac OS. I have made a Mac OSX USB stick, however the bootloader is not recognizing the Mac USB stick. Can anyone help me get a bootloader that recognizes a Mac USB stick?

The bios is software installed on the motherboard and independent of the harddrive and you should be able to access it to set a boot priority for your usb drive.

That sounds about right. If Froghair’s suggestion doesn’t work, try reading this first. The rEFInd Boot Manager
it’s a bit of a read. Remember measure twice, cut once.
Have you verified your macOS is still intact?

I think you should hold down the Option key while turning on your computer. You will then be able to choose the boot source. You choose the flash drive and it should be OK.

Ok so I figured out whats going on. There is a firmware update that I never installed that fixes an issue with the system seeing a DVD or USB stick with Mac OSX. I have found the firmware that I need but I don’t know if I can install it in Linux. The file is in a DMG so I used DMG2IMG to turn it into a iso file then mounted it and got the pkg file with the firmware update, but I have no idea if this pkg file can be installed in Linux. When I go to the Firmware app, it shows the firmware update I need, but has install greyed out, suspect because the firmware is proprietary to Apple. Can anyone help me install the pkg or is it hopeless?

In other news I am loving the Linux build. I found Manuskript and as an author it is working quite well for me.

This is driving around. What would I do: Option + R to reinstall macos. After the installation is complete, reboot and hold the Option key while turning it on to select your boot source. If that didn’t work, I would have refinded.