iRestore VS Divise

I also just saw your device, you can use Devisé to tether downgrade. This only needs the ipsw that you can get from Ipsw.me. And you would boot using Ramiel.

Option 1: Inferius (https://github.com/m1stadev/Inferius) Option 2: Divisé (https://github.com/MatthewPierson/Divise) Option 3: Ramiel (MacOS only / https://ramiel.app) All of these should work without blobs.

The 6th gen iPod Touch is vulnerable to checkm8 so it should be possible to downgrade or dualboot it using Divise but be aware it's a tethered downgrade so you'll need your computer with you if the battery ever dies or you turn it completely off but you could use the Sentinel tweak to have it hibernate at like 10 percent battery so it's much less likely to actually die.

https://github.com/MatthewPierson/Divise/blob/master/README.md "there are currently 3 options for tether booting from said computer. The first way is via manually patching and preparing the required files (Advanced users only), PyBoot which is a python CLI script made by me which automates the entire process (Moderate difficultly) and there is Ramiel which is a GUI based applicaiton for checkm8 related tasks/actions (Easiest/Best choice)"

https://github.com/MatthewPierson/Divise exists but it doesn't bypass SEP stuff at the moment

You cannot with IPSWs, you can with SHSH blobs if you saved them, However you can get to 13.7 without SHSH is using Inferius or Divise, it's more like a dualboot but I don't recommend using Inferius or Divise to install 13.7, as these programs may brick your device.