What's wrong with just Android?
It's difficult to just do things. Even windows feels more "free." Phone OSes are built like prisons.
Ideally Android would let you drop into a real shell, without having to deal with android sandboxing.
Regardless, I use termux and tasker to get my automations done.
And also malware.
That blast radius coupled with (non-Android) Linux's atrocious security is a far worse option
AUR isn't a traditional repository but more functions like a paste bin for package build scripts you have to go out of your way to enable and use at your own risk. It is not how actual Linux repositories work which are way more safe than google or even apple app store.
Probably because of how people submit directly to the commercial app stores and the app store staff are expected to accept them as long as no malware or other problems are detected. Such problems are generally explicitly listed on Terms of Service and app submitters may be able to dispute rejections. Meaning problems generally need to be concrete and justifiable. Also, because of the sheer number, problems are likely scanned for, rather than each app being personally considered by a developer.
FOSS distro package repo maintainers generally don't have any such pressures. They get their absolute pick of what to include from the wild, only taking as much as they're able to handle.
Also, distro repo maintainers handle the building from the source code themselves, while app store apps are closed source to the app stores. Their ability to inspect apps is very limited.
It's a pretty big sandbox in my experience.
How easy it is to do an equivalent thing on Android?
The neat thing about non-Android phones with respect to what you mention is that you can do those things just like how you would on any other computer, without having to worry about Android workarounds that may one day stop working via an update.