brew cannot find ANY packages - macos

Question

I just got my Mac Pro from the shop after hard drive failure. I am trying to install my environment again.
I installed homebrew from the current link on the homebrew website:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
but I cannot install ANY package. Brew cannot find ANYTHING.
~ brew install rbenv
Error: No available formula with the name "rbenv"
==> Searching for a previously deleted formula (in the last month)...
Error: No previously deleted formula found.
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching taps...
==> Searching taps on GitHub...
Error: No formulae found in taps.
What is wrong?

Answer 1

I had the same issue and I was able to solve it by running the doctor command and follow the steps which need to be updated there.
My homebrew-core was not at the master branch.
brew doctor
git -C $(brew --repo homebrew/core) checkout master
And that's it. After that, I was able to run the rbenv install command.

Answer 2

brew search result
$ brew search rbenv
==> Formulae
rbenv rbenv-bundle-exec rbenv-chefdk rbenv-default-gems rbenv-vars
rbenv-aliases rbenv-bundler rbenv-communal-gems rbenv-gemset rbenv-whatis
rbenv-binstubs rbenv-bundler-ruby-version rbenv-ctags rbenv-use
install rbenv
$ brew install rbenv
==> Downloading https://github.com/rbenv/ruby-build/archive/v20200819.tar.gz
==> Downloading from https://codeload.github.com/rbenv/ruby-build/tar.gz/v20200819
######################################################################## 100.0%
==> Downloading https://homebrew.bintray.com/bottles/rbenv-1.1.2.mojave.bottle.tar.gz
######################################################################## 100.0%
==> Installing dependencies for rbenv: ruby-build
==> Installing rbenv dependency: ruby-build
==> ./install.sh
==> Caveats
ruby-build installs a non-Homebrew OpenSSL for each Ruby version installed and these are never upgraded.
To link Rubies to Homebrew's OpenSSL 1.1 (which is upgraded) add the following
to your /Users/rchen/.bash_profile:
export RUBY_CONFIGURE_OPTS="--with-openssl-dir=$(brew --prefix openssl#1.1)"
Note: this may interfere with building old versions of Ruby (e.g <2.4) that use
OpenSSL <1.1.
==> Summary
🍺 /usr/local/Cellar/ruby-build/20200819: 509 files, 253.6KB, built in 5 seconds
==> Installing rbenv
==> Pouring rbenv-1.1.2.mojave.bottle.tar.gz
🍺 /usr/local/Cellar/rbenv/1.1.2: 36 files, 65KB
==> Caveats
==> ruby-build
ruby-build installs a non-Homebrew OpenSSL for each Ruby version installed and these are never upgraded.
To link Rubies to Homebrew's OpenSSL 1.1 (which is upgraded) add the following
to your /Users/rchen/.bash_profile:
export RUBY_CONFIGURE_OPTS="--with-openssl-dir=$(brew --prefix openssl#1.1)"
Note: this may interfere with building old versions of Ruby (e.g <2.4) that use
OpenSSL <1.1.
version test
$ rbenv --version
rbenv 1.1.2