I think that anybody legitimately wanting to get by with just one rifle really needs to load their own ammo to get the versatility out of it. If you're only going to work with factory offerings, a lot of what you want to do with it will be less than optimal.
People shoot in different ways. Some enjoy lying in a paddock for hours plinking at paper, steel or cans, some enjoy hitting steel gongs at distances further than they can see, some enjoy walking creek banks taking running rabbits and foxes, some enjoy sitting in a hide taking ducks and birds out of the sky, some enjoy spending several days and nights stalking deer in steep dense bush, some prefer to stay in a vehicle and use a light to take foxes at night, some enjoy shooting military or other "collectible" rifles, some enjoy recreating even earlier shooting with blackpowder rifles, and some prefer to fit into very specific classes of competition. If you do want to shoot a specific form of competition then your choice of "one rifle" to do everything is going to be greatly restricted to what is eligible for that competition.
To find a single longarm that lets you do all of this, and more, is very, very difficult. A mid-range centrefire, and the ability to load your own ammo can do most of these things very acceptably. Something accurate with a tight twist-rate in the 7mm to 8mm range, offering velocities from 2400fps with the heaviest bullets to 3500fps+ with the lightest, can be very versatile indeed. You can also cast bullets to make for very cheap plinking and to take care of the jobs that you would normally reach for a .22LR to take of.
If you're into ducks though, then you have to use a gun by law (rifles are not allowed), greatly restricting what other duties your gun will do with a degree of competency. You can use chamber inserts to shoot a variety of cartridges, with acceptable results as long as the distances are quite short. You can use a rifled choke and slugs to make it reasonably capable as a deer rifle (not allowed to use shot on deer in Victoria) out to 100m or a little further. You can buy or make longer rifled barrel inserts that turn a 12ga. barrel into a reasonable rifle barrel in .22Hornet, .30-30, 7.62x39mm and .45-70 at the most potent end - rimfire and pistol chamberings are more common. This is a 12ga. .30-30 18" barrel insert for example -
https://chaszel.com/product/30-30-shotgun-adapters/ With a QD scope mount you could see decent accuracy - but it is still a significant compromise over a rifle. In some states, such a barrel insert is considered another barrel or even a firearm in its own right, thus making it void for this example of "one gun". It's also an option to load shot into large-bore cartridges, like .45Colt, .44Mag, .444Marlin and .45-70, giving .410-like loads, but being rifled barrels the range is very, very limited.
So, to be able to effectively choose "one gun/rifle" you first need to determine the purposes you want to be able to use it for.