Mr. Nelson,
That did it! I patched the header and rebuilt u-boot. I had started down a few other paths with investigating kernel config options for LL debugging and MMC support etc. but will leave the kernel config for another time.
Now on to finding the root password for debian 9 and see if I can get the mpd package i want.
Thank you for your expertise, and for the prompt reply.
BTW I came across your ubuntu info (see link below) and it also failed to boot the BB C4 but at the “Loading Ramdisk to 8fc34000 end 8ffffaea …” which I assume is the same memory span issue you found and fixed. If so here is a friendly reminder to give attention to fixing the pre-built image(s) (unless that is automatic in your build system etc. when the patch is pushed).
https://elinux.org/BeagleBoardUbuntu#Method_1:_Download_a_Complete_Pre-Configured_Image