I installed openSUSE Tumbleweed (Snapshot 20200528) on a Raspberry Pi 3 Model
B+ using the DVD image (on a USB stick) to a microSD card in the mmc slot.
Installation went through normally, but it didn't produce a bootable system.

The cause of the issue turned out to be that the boot partition on the microSD
card had not been set up properly - neither U-Boot nor the Raspberry firmware
had been installed on it.

The following email thread contains the original problem report, and the
feedback I got that eventually allowed me to resolve the issue manually:

https://lists.opensuse.org/opensuse-arm/2020-06/msg00010.html