It's fine to have the -devel packages with the unversioned .so files conflict (which they should be explicit about). You're removing an existing soname from EL7 which should be avoided if possible, which it is.
They cannot be co-installed without changing the library name.
Still broken because sundials2 provides names like 'libsundials2_nvecserial.so.2()(64bit)' instead of 'libsundials_nvecserial.so.2()(64bit)'.
Unversioned libraries conflict without renaming libraries in
Could we modify Octave to point to
I installed avogadro2-1.91.0-1 and it runs fine with basic testing. avogadro2-1.91.0-1's Help - About window shows Version: 1.90.0 AvogadroLibs Version: 1.91.0 Qt Version: 5.11.1 and the top window bar shows Untitled - Avogadro 1.90.0. I'm unsure if the interface version should be 1.90.0 or 1.91.0.
It's a known bug.