The AC2100 and r2100 are very similar to r3g router. There are few users that were able to get out of soft brick: here is one, here is one post suggesting:
with the stock bootloader , you just have to download official firmware, rename it to miwifi.bin, unplug mains,plug usb, press reset until i say so, plug mains , keep presing reset until led flashes orange , leave reset button, wait until led is blue. and your router is recovered
You may try putting the file (instead of USB) on TFTP server and sending it to bootloader.
By the way, debricking AC2100 / R2100 should have it's own topic IMHO.
@emirefek
The images you posted are great.
You can get 19.07 images from here:
https://drive.google.com/folderview?id=13mTGEswOK_YABMWrE8TbLoKqCgCqTEmL
I'm running it for a while and it works flawlessly for me.
Thank you very much, your work is very appreciated!