Linux

It's a choice. We know that it's riskier to use stuff from AUR. Which is why it's highly recommended to read the PKGBUILD before installing the package. The basic Arch install doesn't even include an AUR helper. That said, AUR is typically very reliable for packages with a decent userbase. It's mostly due to the community aspect. Bad actors are caught relatively easily as the PKGBUILD is available to look at.

Any major Linux distribution has a system for building packages

I have built packages for all the major ones. Non arch packages are a pain to build and I never want to do it again. In contrast arch PKGBUILDs are quite simple and straight forward.

How can you trust code with root access to the system just because it’s in the aur repository?

Because you can view the source that builds the packages before building them. A quick check to not see any weird commands in the builds script and that it is going to an upstream repo is normally good enough. Though I bet most people work on the if others trust it then so do I mentality. Overall due to its relative popularity it is not a big target for threats when compared to things like NPM - which loads of people trust blindly as well and typically on vastly more important machines and servers.

It's amazing that people criticize Windows security with .exe's and then install packages from external repositories with the security of "trust in the repository".

As with almost every case of these sorts of comparisons, these are likely separate groups of people holding separate groups of opinions.

I don't use Arch anymore, but when I did I found that the AUR was really useful to quickly install niche applications that would take ages to be approved on to an official repository. Often those would be made by the application developers themselves or members of the community. I would personally vet the packaging script myself, but I'm sure many wouldn't - and that's fine. As with most software, there's some trust involved and often you assume that if you're installing from a reputable repository it's going to be fine. If people aren't vetting the installation scripts and are installing from random repositories, that's really their problem. I'm glad the possibility existed and it's the one thing I've missed in distros I've used since then.

Not sure if sarcasm or actual disinformation. You're not supposed to trust the aur, that's kinda the whole point of it. The build scripts are transparent enough to allow users to manage their own risk, and at no point does building a package require root access.

Well there is far less malware on Linux tbf so comparison is not completely accurate. But same caution applies, try to vet and understand what you install. That part is also easier with the AUR as it's transparent in the packagebuild what it does unlike random exes with closed source. It's also a large community with many eyes on the code so unless it's a package with few users then it's gonna get caught pretty quickly.