Thanks for your input. I know its OEM log, the working OpenWrt firmware broke after using attended sysupgrade from 22.03.5 to 23.05.3. The device is to old for Xiaomi service.
Last year i went back to OEM firmware without issues. This time no luck.
I found two more topics with the same boot-problem, from 2020:
Debrick Mi Router 4A Gigabit
Xiaomi Mi Router 4A Gigabit Edition (R4AG/R4A Gigabit) -- fully supported and flashable with OpenWRTInvasion - #1428 by BillBluescreen