Support.apple.com/mac/startup -2006f. Mac Air early 2015

Follow these instructions: How to create a bootable installer for macOS - Apple Support

What macOS version is that other system running? Try downloading OS X El Capitan and creating a bootable installer with it.

The error you are encountering -2006f suggests an inability to download macOS from Apple with that machine, which can occur for a number of reasons. Network communication failures, that sort of thing, and if that won't work you need a USB boot drive. It seems everything you did is leading up to the need to contact Apple:

"If you still need help, please contact Apple Support."

Does the screen resemble the following?

Excerpted from If your Mac doesn't start up all the way - Apple Support:

"A globe with an exclamation point means that your Mac tried to start up from macOS Recovery over the Internet, but couldn't. Learn what to do if your Mac can't start up from macOS Recovery."

That link takes you to "If you see the globe and alert symbol, try these solutions." Proceed with each of them, eventually concluding with

"If you still need help, please contact Apple Support."

i made boot usb drive last night is there key I hit to get it to boot the usb drive

"Use the bootable installer" in How to create a bootable installer for macOS - Apple Support describes what to do.

A 2015 MacBook Air has an Intel processor.

It's looking for an input device (mouse or trackpad), which means its built-in trackpad is not being recognized.

Try resetting the SMC: How to reset the SMC of your Mac but I doubt it will help. All the more reason to contact Apple Support.

I understand you can install Linux on the Mac's internal startup drive, and boot from it. Is that correct?

You seem to be encountering two separate problems, the most recent of which is that the "bootable installer" doesn't work. Specifically, holding an Option key does not convey the ability to select the flash drive as a boot device. If that is also correct, it's a separate problem you need to fix.

Confirm that you followed these instructions: How to create a bootable installer for macOS - Apple Support. You will need a working Mac running an appropriate macOS version to do that. In other words forget about using a PC; that won't work. All I can tell you is that I have followed those instructions and can confirm they work exactly as described. If it helps, you can refer to this Discussion for a step-by-step description of how I create these installers. Just change the macOS system name from Sierra to the version you are installing though.

You will probably also want to partition the internal storage volume. Unless that has already been accomplished, you might need to erase the entire device. You can use the "bootable installer" to do that, but it has to work (obviously).

With Macs the only way to install macOS on a completely empty startup volume is through Internet Recovery, the bootable installer you're trying to use, or Netboot — which is not an option for Macs newer than yours.

That's it, unless your Mac is so old it incorporates an optical drive — and the MacBook Air never had one of them.

Internet Recovery should have worked: "If your Mac can't start up from its built-in macOS Recovery system, it might try to start up from macOS Recovery over the Internet." As that document explains, the -2006f error you originally described may have been temporary; an inability to contact Apple's servers for whatever reason. It may also occur if you are using that Mac in a region or country for which that Mac was not originally sold... but it's a moot point — if Internet Recovery doesn't work and the startup disk's internal Recovery partition has been erased or is missing you're basically stuck.

The only remaining practicable option is USB.

Definitely call Apple, but don't be surprised if they recommend you make a Genius Bar appointment. It's probably a hardware fault that only Apple or an authorized Apple repair facility will be able to fix.

It might be a simple fix, but the diagnosis ought to be free.

Still the same problem, and it's not likely the SSD was the cause. You don't need anything on the startup disk to use Internet Recovery, but you're not even getting that far.

The inability to detect an input device is a show-stopper. You won't be able to select the flash drive and use the bootable installer.

I understand you are unable to boot and run Linux from the flash drive, but you can install Linux on the SSD and boot from that. Is that right?

I do not know the reason Linux will not run on the flash drive itself, but if my understanding is correct, I'd be satisfied with that result.

It has been a long time since I attempted to boot and run a Linux system from a flash drive, but it has a lot of limitations that made it an unattractive option compared to the dual boot system I eventually settled upon.

It is possible that Internet Recovery won't work unless you are in a region where it is supported and / or compatible with the region for which that Mac was sold.

macOS is based upon FreeBSD, which in itself is not Unix either but a Unix derivative. It has evolved from FreeBSD to a great extent, and most of macOS is proprietary Apple. Many Unix commands work identically, and macOS looks very familiar to anyone accustomed to Unix, but they are definitely not one and the same.