There will be official Installation image fro Manjaro Linux also.GT-R will also come with Manjaro Image pre-installed for users to use it directly without the need to any hassle of installing Linux manually.
Beelink GTR7 (7840HS) - Manjaro Linux
Beelink SER5 (5600U) - Manjaro Linux
Beelink GT1 Ultimate (S912) - Libre Elec TV
Beelink GT King Pro (S922X-H) - Manjaro ARM Linux
Beelink GS King X (S922X-H) -
Download and install balenaetcher software from https://www.balena.io/etcher/ and write the iso image you downoaded previously to an appropriate usb. insert the usb to GT-R, boot GT-R device select to boot from usb first. you need learn the key to select boot device normally it is F11. Just try to find it.