I've put in about an hour at this point, and I'm starting to feel a bit dead inside.
I started by downloading
ungoogled-chromium version 71.0.3578.98-2 from GitHub. I extracted the
tar.gz file into my home folder. Then, using the instructions from the "Any Linux Distribution" section of the build instructions. I followed the instructions to the point of adding the LLVM APT repo. I added the specified lines for Bionic (18.04) to my
/etc/apt/sources.list file, retrieved the key with:
wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - sudo apt-get update
This output these errors which look like this:
E: The repository 'https:/dl.winehq.org/wine-builds/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. W: GPG error: http://apt.llvm.org/bionic llvm-toolchain-bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 15CF4D18AF4F7421
I then, (though I knew it wouldn't work), ran:
sudo apt-get install clang-8 lld-8 llvm-8-dev python python3 ninja-build
and all of the LLVM packages were not able to be installed.
This is my first experience building from source, so I know inevitably made some obnoxious novice mistake.