There is Ultibo based bare metal Oberon version too: https://github.com/MGreim/ultiboberon

BTW This is essentially a port of a very early version of the Oberon operating system. Later versions got much fancier.

This early version was described by Wirth in his 1992 book "Project Oberon: The Design of an Operating System, a Compiler and a Computer". After his retirement he prepared a new edition of this book, for which he ported the system to a custom RISC architecture. (The original targeted the now extremely obscure NS32000.)

I think this Oberon Pi is just a standard Raspberry Pi Linux distro with an emulator for this architecture preloaded.