it turns out it was a mix-match between installed versions of Houdini on my VM.
Reinstalled 18.5.351 and everything seems to work as expected.

I should stop installing bazillion of beta versions on the same machine where I'm supposed to work...

I opened a new terminal and sourced my Houdini 18.5.391 environment
I typed 'hython' and got the same error
hython
Houdini DSO error on '/netapp/Octane/Octane_2020.1.5.2_Houdini_18.5.351_Linux_gcc6.3.1/dso/Houdini_Octane_18.5.351.so'
libHoudiniUI.so: cannot open shared object file: No such file ...

I've a simple Houdini 18.5 scene with one model, a camera, an Octane material and an Octane ROP

Triggering the single Octane render from the Octane ROP works as usual.

I've setup a simple TOP wedge node to alter the geometry shape.
I want to render short sequences with Octane for each model wedge ...