This is a good question. There's nothing I hate about Linux there are things I hate about some projects, and some communities, and some distributions.

Maybe zombie processes. I guess I dislike that Linux isn't a microkernel, but I doubt it'd have a huge impact because the kernel has been incredibly stable for my uses for years. I can't actually remember the last time I saw zombie processes, but it was within the past two years, and their existence is just a fundamental stupidity in Linux, and closely tied to the monolithic kernel architecture.

But, still... it'd be hard to stretch that to "hate."

CUPS is a terrible piece of software that almost everyone needs, and needs somebody to come along and do a pipewire on it. I guess I hate CUPS, but that's not Linux.

nuts could be much, much easier. It's designed for power users and is a PITA to configure. Quite capable, but could be a lot more simple for simple use cases.

I'm really reaching here. There's little in Linux + BSD userspace (or even GNU) that's not far worse on a Mac or in Windows; maybe I'd feel stronger if there was a better option.

I'm really, really hoping Redox makes it. I'd love to see an end-user oriented, non-research microkernel with broad hardware support - something good enough to run on modern bare hardware. Then I might jump ship, especially if I get to jettison systemd in the process.