There is also a completely different way, a camera which indirectly projects onto a mesh as a texture. I asked about it here:
This mesh would of course move with the main camera(s) movement. It just needs a mesh with a UV, most likely a plane
It is also VR / XR friendly. If you put the mesh into BILLBOARD mode, there is a new one for XR, it would make it more visible. Also pretty efficient in that the texture stays in the GPU, to then be attached to the mesh on later renderings by the main camera(s), multiples for XR.
Not what was really asked for, but one might make into an occasional sign / map, to show where you are. In today where everyone is being lead around by the nose with GPS, might make for something more interesting to only be available at certain times. Would kind of be a cool having your actual avatar being in the actual sign “marking you are here”.
Other wild effects possible. Like a fun house mirror using a backwards, distorted UV. Probably need something with a UV editor, Blender, to make that, but still.
I am using it as more a maxmap than a minmap, but that is just a very close camera, projected onto a large mesh.