Downgrade a jailbroken Kindle 10th gen from 5.15.1

Hi there,

I have a jailbroken Kindle 10th gen that, due to a temporary deactivation of the renamed OTA files, upgraded to firmware version 5.15.1

I still can ssh into it, but am unable to "install" KUAL (the kindlet doesn't show up).

I'd like to know if there's a way to manually downgrade it back to 5.14.2 (or earlier).

Thanks a lot.