> Homebrew asks users (on Intel macs) to change the ownership of /usr/local to their local user.

Nope - intel Mac on Big Sur:

drogers@SJCMACJDYMD6M ~ % ls -l /usr

[snip]

drwxr-xr-x 15 root wheel 480 Dec 14 20:10 local

[end snip]

And for the record, neither of your links support your claim.

This changed in the last few years (I don't recall the exact date), but it absolutely was the way that brew operated for many years.

https://apple.stackexchange.com/questions/1393/are-my-permis...

https://superuser.com/questions/1264673/chown-usr-local-oper...

>Any chance you're on Apple Silicon?

No, I'm on an Intel chip, not M1.

>Homebrew asks users (on Intel macs) to change the ownership of /usr/local to their local user. And it refuses to run under sudo.

Again, no, not on my machine it doesn't. /usr/local is root:wheel. This is a newish (to me) machine that I gave first birthday to beginning of December 2020. The first thing I did was installed brew and started installing the things that makes my computer useful to me. No permissions were asked to be changed.