<freem>
oh, I should have tried here before sending a message on forum. Well, too late. Anyway, let me quickly repeat myself here: a recent commit for the GTK4 preparation inverted the behavior of mouse wheel in solvespace. Reverting "31d0c27 Handle smooth scrolling" and "a17fb15 GTK: Handle smooth scrolling according to the documentation" fixed the situation for me.
<freem>
I would have done a github issue on this, but I deleted my account when they decided to annoy me with their forced 2FA spamming my mailbox, so used the forum instead.