I was pleased with the CLI install notes provided by GrapheneOS and found them to be more than sufficient, and was able to get GrapheneOS loaded onto a Pixel 4a without issue. Presented below are the notes I produced while getting it installed. While I played around briefly with getting it installed from my Windows 10 machine, the fact is that my Linux machine had most of the pre-requisites in place to get the install done and it was just easier to work from it.
sudo apt install libarchive-tools curl -O https://dl.google.com/android/repository/platform-tools_r30.0.5-linux.zip echo 'd6d72d006c03bd55d49b6cef9f00295db02f0a31da10e121427e1f4cb43e7cb9 platform-tools_r30.0.5-linux.zip' | sha256sum -c bsdtar xvf platform-tools_r30.0.5-linux.zip export PATH="$PWD/platform-tools:$PATH" fastboot version 30.0.5-6877874 sudo apt install android-sdk-platform-tools-common fastboot flashing unlock sudo apt install signify-openbsd alias signify=signify-openbsd curl -O https://releases.grapheneos.org/factory.pub cat factory.pub - make sure it matches (https://twitter.com/GrapheneOS/status/1145259815851253762) curl -O https://releases.grapheneos.org/sunfish-factory-2021.01.23.03.zip curl -O https://releases.grapheneos.org/sunfish-factory-2021.01.23.03.zip.sig signify -Cqp factory.pub -x sunfish-factory-2021.01.23.03.zip.sig && echo verified
bsdtar xvf sunfish-factory-2021.01.23.03.zip cd sunfish-factory-2021.01.23.03 ./flash-all.sh
fastboot flashing lock
As your phone boots, you’ll notice the GrapheneOS splash screen – you’re finished!