That changes just what reality is, what thing you are trying to understand. It is no longer something outside and independent of your mind but your mind itself and the things within it. Your mind would become the objectively real thing and you could still study the structure of your consciousness, of your experiences, what causes the regularities in them we call the laws of physics and so on.
We essentially just decided to ignore most of such possibilities most of the time, from solipsism as you mentioned over Last Thursdayism [1] to living in a simulation or the Matrix. They may seem interesting to ponder about at times but in the end they just prevent you from learning anything at all. You can always come up with a strange scenario in which anything you might believe turns out to be falls.
That certainly sounds kind of arbitrary and unscientific, but without some founding assumptions about reality you get nowhere and that is of course not helpful at all. We should certainly keep an eye on those assumption and we do, living in a simulation for example pops up quite frequently, but for the moment our success seems to justify our assumptions.
[1] The world came into existence last Thursday in precisely the state of last Thursday with all the memories and evidence of the time before last Thursday just to fool us.