I'd like to install GrapheneOS via the Arch Linux based distribution Manjaro Linux using the CLI installation guide. The guide states that fastboot as currently provided by Arch Linux is not usable and that standalone platform tools need to be installed. However, in the corresponding section of the guide, there are no instructions for Arch Linux. Could anyone please provide the commands to download, verify and extract the standalone platform-tools on Arch Linux ? Thank you.

I installed on Arch (not Manjaro) with the android-sdk-platform-tools package from AUR.
Worked for me 2 months ago.

Don't read this as a recommendation, because official docs don't approve it.