Here is a good exapmle to install manjaro on pi-5 (rapsberrypy 5).
But you should have pi-4 (rapsberrypy 4).
I have installed manjaro to my pi-5 this way a few days ago.
I am using hyprland and it works fine.
https://forums.raspberrypi.com/viewtopic.php?t=367491
The key to me was update manjaro software stable rpi4 first and change to unstable branch later and then install software.
outline of this method.
0. I have manjaro-arm rpi4 on SD-card in my pi-4.
1. update pi-4.
2. move to unstable branch.
3. install kernel & some pkgs etc.
4. modify some setting parameter; overclock etc... if you need.
5. set updated SD-card to pi-5 and run.
If manjaro already supports pi-5, please let me know…