Hello,
You have to know that in his normal and default behavior the stock filter with "in stock" will take ALL product quantity (>0) AND unlimited (-1)
That's a logical way to proceed because unlimited, means available.
And so, your question isn't logical,:
"I needed it to work also for -1 (unlimited quantity)."
because by default must be the default way to proceed, and so idea judgement isn't the point...
But maybe there is for some reason a bug ?...
I note that you have some
override on your filter view, can you try to
remove (after save it on your side) this override?
If after this, your filter behavior is corrected, that's mean that your override
make something wrong.
This point isn't easy to understand:
"Is it possible to make filter "instock" to apply on quantity -1 and 0"
So you mean
in stock =>
0 stock ?...
Well, maybe tour have a precise purpose or context but just this is difficult to understand.
Awaiting news from you.
Regards