So there is something not quite right with my current Apache setup and HTTP/2:
Dec 1 15:44:14 zicke kernel: [776008.255216] apache2: segfault at 1 ip 00007fcb80f95646 sp 00007fcb66767798 error 4 in libc-2.27.so[7fcb80ee4000+1e7000]
This causes strange loading errors with this blog and the others hosted at weblogs.at.
Thus, I disabled HTTP/2 for now until further investigation. It looks similar to this bug report but I am not using the PHP module…