I have the same issue

==> Downloading https://ghcr.io/v2/homebrew/portable-ruby/portable-ruby/blobs/sha256:720d4fb1164e600f787d656019a8e46314dc38e1885f4a8df809c180acf5e7b3 ################################################################################################# 100.0% ==> Pouring portable-ruby-3.3.6.el_capitan.bottle.tar.gz /usr/local/Homebrew/Library/Homebrew/cmd/vendor-install.sh: line 227: 11111 Killed: 9 "./${VENDOR_VERSION}/bin/${VENDOR_NAME}" --version > /dev/null Error: Failed to install ruby 3.3.6! Error: Failed to install Homebrew Portable Ruby (and your system version is too old)!

I'm running MacOS 15.1.1 6 Core Intel Core Processor