Hello Ste,
thank you for encouraging me to update the ngspice DLL
On the ngspice repository I found the newest ngspice engine, version 32. I extracted the DLL as per the instructions in the tutorial file mentioned earlier and replaced the older one in the KiCad\bin folder.
And bingooo 
it solved my problem!
The LMV358 Sallen-Key low pass filter now looks correct:
And I can confirm that the Alternate node sequence defined in the opamp’s Spice Model Properties is taken into consideration correctly (I used commas as separators).
Thank you guys for your help. I would have been lost without you!
Considering that your help is completely voluntary, as is the software, I understand that such support cannot be taken for granted.
This is where I tend to agree with @BlackCoffee: I generally like to pay a (reasonable) fee for any good software, because I know that development and support cost a lot of time and someone has to pay for it. Hardware people (like me) get paid for their job, so why should software developers work for free? I mean, everybody needs some cash for his/her living.
But probably this is a rather philosophical and out-of-topic discussion.
Thank you anyway!