I run Tumbleweed on several RPI4 boards for some time, and now (couple of months ago) I observe crasy behaviour of the boot proccess. The boot starts normally, but ends just after the "U-Boot>" message is written on the screen. After that, boot loader writes several rows of random characters and freezes. If the board is cold (i.e I power it down, wait couple hours and power it up) the boot proccess usually continues normally on the cold board. I also tried several MicroSD cards (difernt types, speeds, sizes, vendors ...) with the same result. The behaviour is the same on 4GB and 8GB boards. I didn't notice the exact date when this started to happen (since it does not usually apear on the cold board). At the same time when OpenSuSE hangs up, the original RaspberryOs and also DietPi OS boot normally (i tried it many times). If the boot is successfull, everything works normally until restart.