I would guess probably not, because there's a lot of platform specific code in it. It was originally tested on Switch by removing all the platform specific code beforehand.
I think it has a decent chance of working but it all depends on which WebKit version the Wii U is using. I'm sure it's pretty old, but it might be too old for Pegasus to work, since bugs are often introduced in a specific version and then later fixed.
I don't know if anyone knows what WebKit version the Wii U is using or what versions Pegasus supports, but by knowing both of those it would be easy to tell if it's likely to work or not.