Both of these are effectively the same damn thing but everyone loses their minds over the first one.
Also, a lot of those install scripts do check signatures of the binaries they host. And if you’re concerned that someone could have owned the webserver it’s hosted on, then they can just as easily replace the public key used for verification in the written instructions on the website.
If it points to mirror.ubuntu.com, it'll be mirroring at host end, instead of inside apt. But as apt does do resolution to a list, it'll be fetching from multiple places at once.
> I’m always a bit shocked how seriously people take concerns over the install script for a binary executable they’re already intending to trust.
The issue is provenance. Where is the script getting the binary from? Who built that binary? How do we know that binary wasn't tampered with? I'll lay odds the install script isn't doing any kind of GPG/PGP signature check. It's probably not even doing a checksum check.
I'm prepared to trust an executable built by certain organisations and persons, provided I can trace a chain of trust from what I get back to them.