The ISO does work - albeit not for your hardware combination - so there is that - most likely it is graphics related.
You need to pull up your sleeves and get to work.
Can you boot the ISO to the GRUB selection screen?
If yes - then press e on the default selected entry - as we need to verify if you can get onboard the console of the live system
Append a space and the number three (3) to the kernel command line arguments and press F10 to load the kernel.
This verifies that you can actually load the kernel when you reach the console (press escape to remove the plymouth screen).
If you get this far - I recommend installing a base system.
Login as root using passwd manjaro
install a base system
This can be done complete manual or using architect.
A manual install will use some unconvential combination of pacman arguments to avoid pulling updates for the ISO itself as this would be pointless and waste of time.
By hand
A completely manual installation is a series of steps outlined in [root tip] [How To] Do a manual Manjaro installation
Using architect helper
-
Select a useful mirror
pacman-mirrors --continent -inavigate using arrow and tab - select an appropriate mirror - and click OK
-
Fetch package databases
pacman -Sy -
Install
manjaro-architectpackagepacman -S manjaro-architect -
Launch the helper script
setup
The point of going through this is be to establish status points.
Workable system states - where you add functionality - testing - confirming - undo or continue with next step.
With the Architect helper script you can install either a base CLI system and work from there.
You can Install a Manjaro branded Plasma or you can install a default Plasma - your choice.
In any case - you will have a working core system - and further troubleshooting the GPU will be a lot easier with a working core.