simple 15.5 x64, on rather old amd hardware but worked fine in 15.5

system has come a long way with upgrades from previous leaps
with a single sata HDD
completely updated in 15.5 before
then zypper via releasever=15.6  and zypper ref and zypper dup,
download-in-advance.

upgraded thousands of packages, then rebooted. then never came back alive.
looking at the machine physically, I see it in a kernel panic error message
telling me

(copy paste from a photo/picture, text OCR, sorry for errs)

---------

0.63410711

T11 Kernel panic not syncing: UPS: Unable to mount root fs on
unknown-block(0,0)

711 CPU: 2 PID: 1 Соми: змарриг/6 Not tainted 6.4.0-150600.16-default #1
SLE15-SP6 38db936c6f7776667f67c71a8b5f453a65a8919f

0.63428110

T1] Hardware name: Systen manufacturer Systen Product Name/F2A85-U PRO, BIOS
6503 07/10/2014

0.63452011

0.63470611

T11 Call Trace:

T1] <TASK>

0.63476831 8.63482311

711 dump_stack_lul+0x44/8x69

0.63491710

T11 panic+0x189/8x2c0

8.63499211

711 mount_root_generic+0x114/9x110

0.63508810 8.63517311

T11 ? mount root+6x146/9x190

0.63528811

T11 7 pfx_ignore_unknown_bootoption+0x10/0x10 T11 prepare namespace+8x1a6/8x200

0.63538210

Til kernel init_freeable+0x25c/8x298

8.63540110 0.63557410

Til?pix kernel_init+0x10/8x10

T11 kernel Init+0x16/0x130 fron_fork+0x2c/0x50

8.63565511 Til ret

TLI TASK

0.635739][

6.63585511

Til Kernel Offset: 0x1f660000 from 0xffffffff81000000 (relocation range:
6xffffffff80000000-0xreeeeeerbeeeeeee)

6.63667411

T1]-[end Kernel panic not syncing: UFS: Unable to mount root fs on
unknown-block(0,0) 1

-----------

grub2 bootmenu appears fine, I didnt try safe modes or other stuff there just
yet. I tried another boot (ctrl alt del) but it ends up in the smiliar or same
kernel panic, sometimes other cpu cores shown.

thanks.