Tipoc - I'm curious (and serious.) How do you adapt to a right-hand bolt action rifle (iron sights or scope?)
I didn't answer completely because I had some household duties to attend to.
This opinion doesn't take into account glasses, or bi-focals, those add a twist but not an unsolvable one.
With long guns, keep in mind that as with handguns there are different uses for the guns. Different sports or uses allow for different options.
For hunting, for sighting in a rifle or two at the range, and other situations whether with scope or iron sights it works to simply close the dominant eye and focus with the non dominant. Think of strong right hand and strong left eye, the rifle comes to the right shoulder. Close the dominant eye and look through the sights or scope with the weak. I know and have known members of SWAT teams (in Del Norte Co. and San Mateo Co. who use this method, one a police sniper.) It's older than dirt and works.
For extended sessions with rifle, as in bench rest competition or competitive accuracy matches, the "close the eye" method tires the eye too much and produces strain. A blinder on the shooting glasses or patch over the dominant eye works very well.
This is also possible in skeet.
It's difficult to stalk game through woods, or compete in 3 gun competition while wearing a patch or having the eye covered.
When a person who is right handed and right eye dominant shoulders a carbine with iron sights or scope and keeps both eyes open, their brain simply ignores the information coming from their non dominant eye. You can only focus through sights or scope with one eye. Stereoscopic vision plays no role when peering through a scope. The information processing from the other eye falls into the background, becomes irrelevant. This is the norm. The exception will be in combat, snipers excluded.
Some individuals learn to simply ignore the information coming from the dominant eye while using a scope or iron sights. It can be done but not everyone can do it. It's handy but not needed.
In target competitive shooting, with handgun or long gun it's not unusual to see some shooters, even those not cross dominant, put a patch over the eye that's not using the scope to reduce eyestrain and enhance the focus.
This is what I mean by adapt.
Others have already gone over the turn the head slightly method with pistols. it's what I do for defensive shooting, along with point shooting at close range.
tipoc