Thanks for your hints
Sorry for my late reply, I didn't get a message about new posts in this thread after the first reply arrived.
No, I'm not deterred. The official sample files are no focussed on beeing "minimal".
Bad luck for me, that "minimal valid code" is not a popular start point. I like it "bottom up" in other situations too.
Independent of this search for a minimal testcase:
As well I'm looking for a good public valid testcase for my Kobo H2O which demonstrates, where the software of the reader still has bugs/faults.
Nice, if it is an ebpub3 one.
In general about ebub3:
Would you disadvise to use it with Kobo?
I do only talk of manipulated code by myself.