J4105 preempt RT real time kernel patch problem (repost)

(double posted to add ‘odyssey serials’ category)

Hello,

I’m having the hardest time trying to patch/install a preempt RT real time kernel ubuntu
within the seeed j4105.
I’m stuck with the ‘loading initial ramdisk…’ problem.
Tried many how tos, configs etc, to no avail.
Currently using:
linux-4.4.270.tar.xz
patch-4.4.270-rt222.patch.xz

Followed this (and many others):

with salt, since it’s not complete.

Will provide any additional info upon request,
thanks in advance.
Bruno