My work machine is a Mac and I don’t like it. “It just works” is a myth in my experience. In general I’ve no allegiance to any OS and all are welcome. I’m probably most familiar with Linux these days but that’s as much because a lot of the tools I like don’t run well on FreeBSD.
I love my Chromebooks though.
An RPi with openHABian can get you up and running pretty quickly with minimal (not none) Linux knowledge and skills. But if you are willing to spend more you might look at a NUC. That would be way over powered than an RPi but less fiddly when it comes to dealing with the fact the RPi is running off an SD card. IIRC some NUC kits come with an SSD, or you might have a spare one which can make things easy. If not, factor that into the cost. And they can run Windows (though for that matter there is a stripped down version of Windows that can run on an RPi too) so you don’t necessarily need to abandon Windows. You might just have to abandon running OH in Docker on that one machine but can put everything else on your big machine.
RPis are used in industrial contexts. It is definitely “serious” enough to run your home automation. Except for the SD cards, I’ve found them to be really solid machines even under harsh conditions. But SD cards are terrible. They wear out over time and power outages to the machine can corrupt the file system. Though it’s also super easy to swap in a cloned one in an emergency.
But I would never recommend just setting any machine up and not at least periodically logging in and upgrading the OS and related packages. So no matter what you choose, you’ll want to plan for at least that.
Ultimately it’s all what you are comfortable with and/or what you want to learn.