Linux

I know about it. It's pretty popular, so much in fact that you can buy a wide range of routers with it preinstalled.

I've long known about it. I don't seriously use it, but I would if only my Wi-Fi router was fully supported. It's an Asus one (that I got for free from T-Mobile a decade ago) so I installed Asuswrt-Merlin on it instead.

Following the recommendation of homelab communities, I got into OpnSense (a BSD-based firewall system for x86 hardware only) last year, still keeping my Wi-Fi router as a dedicated AP. In hindsight I somewhat regret that choice and probably would've been better off buying a new OpenWRT-compatible router and using it to handle firewall/routing/AP all in one device instead of wasting the power draw of another separate N100 system. I like having wireguard and vnstat in my router now, which Merlin didn't offer, but I know OpenWRT has those too and I don't have any other needs that warrant a higher-power router.

It is fairly easy as for most hardware it is pre configured in a way that makes sense.

Setting it up in a VM is a different story

In my experience it's because it's finicky as fuck and requires very specific (and often more expensive) router models, and even then it still crashes just as much as a proprietary os router.