brew: Brew extremely slow with external taps

brew config output

HOMEBREW_VERSION: 3.0.0-21-g551594e ORIGIN: https://github.com/Homebrew/brew HEAD: 551594e695a6740a6bd9e60ba0e7899d3de9c97a Last commit: 2 hours ago Core tap ORIGIN: https://github.com/Homebrew/homebrew-core Core tap HEAD: bbefd0b98a3e14ba8a5291779900c4878b52b4a5 Core tap last commit: 6 minutes ago Core tap branch: master HOMEBREW_PREFIX: /opt/homebrew HOMEBREW_CASK_OPTS: [] HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.aOl7ufjlWR/org.xquartz:0 HOMEBREW_EDITOR: /usr/bin/nano HOMEBREW_GITHUB_API_TOKEN: set HOMEBREW_MAKE_JOBS: 8 Homebrew Ruby: 2.6.3 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby CPU: octa-core 64-bit arm_firestorm_icestorm Clang: 12.0 build 1200 Git: 2.30.0 => /opt/homebrew/bin/git Curl: 7.64.1 => /usr/bin/curl Java: 1.8.0_271 macOS: 11.2-arm64 CLT: 12.4.0.0.1.1610135815 Xcode: N/A Rosetta 2: false

brew doctor output

Your system is ready to brew.

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• The brew doctor above contains no “Warning” lines.

What were you trying to do (and why)?

Trying to install a package from an external tap.

It takes about 5-10 minutes between ==> Installing ABC from XYZ/123 and ==> Downloading https://ABC.tar.xz

While this is happening, ruby process sees constant 100% cpu usage.

What happened (include all command output)?

Nothing, really. Except, as explained, it takes 5-10 minutes from beginning until brew begins downloading the tarball with sources.

What did you expect to happen?

I expected that it proceeded to download the tarball immediately after issuing the command.

Step-by-step reproduction instructions (by running brew commands)

brew tap kde-mac/kde https://invent.kde.org/packaging/homebrew-kde.git --force-auto-update brew install kmymoney or brew install libalkimia