I uninstalled Homebrew and am attempting to reinstall it. Now I'm getting an error.

[AceAttorneyMaster111]

I uninstalled Homebrew because I migrated to an M1 Mac and the intended location for Homebrew moved, and it was just easier for me to get a fresh install. I ran the uninstall script from the official site, it seemed to mostly work but threw an error when it tried to get rid of a directory, saying it didn't have sudo.

==> Removing Homebrew installation...
Warning: Failed to delete /usr/local/Caskroom
rm: /usr/local/Caskroom: Permission denied
Warning: Failed to delete /usr/local/Cellar
rm: /usr/local/Cellar: Permission denied
==> Removing empty directories...
Password:
==> /usr/bin/sudo /usr/bin/find /usr/local/bin /usr/local/etc /usr/local/include /usr/local/lib /usr/local/opt /usr/local/sbin /usr/local/share /usr/local/var /usr/local/Caskroom /usr/local/Cellar /usr/local/Homebrew /usr/local/Frameworks -name .DS_Store -delete
==> /usr/bin/sudo /usr/bin/find /usr/local/bin /usr/local/etc /usr/local/include /usr/local/lib /usr/local/opt /usr/local/sbin /usr/local/share /usr/local/var /usr/local/Caskroom /usr/local/Cellar /usr/local/Homebrew /usr/local/Frameworks -depth -type d -empty -exec rmdir {} ;
==> /usr/bin/sudo rmdir /usr/local
rmdir: /usr/local: Operation not permitted
Warning: Failed during: /usr/bin/sudo rmdir /usr/local
Warning: Homebrew partially uninstalled (but there were steps that failed)!
To finish uninstalling rerun this script with `sudo`.
The following possible Homebrew files were not deleted:
/usr/local/.com.apple.installer.keep
[...] (lots of files were here)
/usr/local/var/
You may wish to remove them yourself.

I tried to rerun the script with sudo as suggested, but I got an error:

% sudo /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall.sh)"

dyld: Library not loaded: /usr/local/php5/lib/libidn.11.dylib
  Referenced from: /usr/local/bin/curl
  Reason: image not found

So I just removed the /usr/local/Homebrew folder manually.

Now, I'm trying to reinstall Homebrew into /opt/Homebrew and got the same error:

% /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
dyld: Library not loaded: /usr/local/php5/lib/libidn.11.dylib
  Referenced from: /usr/local/bin/curl
  Reason: image not found

What do I do?

[gromgit]

Evidently, only a partial cleanup of previously-installed formulae was done. In particular, /usr/local/bin/curl was left behind, but at least one of the libraries it depends on (/usr/local/php5/lib/libidn.11.dylib) was wiped.

The easiest way around this is to use the system curl, as follows:

/bin/bash -c "$(/usr/bin/curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

[AceAttorneyMaster111]

Should I finish cleaning up what was left behind before I do this? If so how would I go about that?

[gromgit]

Yeah, I guess it wouldn't hurt to run the uninstaller again, this time with the system curl as above:

/bin/bash -c "$(/usr/bin/curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall.sh)"

[AceAttorneyMaster111]

% /bin/bash -c "$(/usr/bin/curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall.sh)"
/bin/bash: line 197: brew: command not found
Failed to locate Homebrew!

:(

[gromgit]

In that case, you should just proceed with the install under M1. Get that settled first, then go back into /usr/local and manually clean up all the files that were mentioned under The following possible Homebrew files were not deleted in your original post.