The 203mm gun is likely to be too powerful for a wheeled chassis - even a 155mm is quite a challenge to mount successfully on a truck. The 203 is so powerful that it requires an alarm to warn the crew to clear the area before a shot can be fired.
(Thinking about it.... ) I agree, the only way to get a 203mm gun on a wheeled chassis would be to have a reduced power 203mm gun, which pretty much defeats the entire purpose of having a 203mm gun really.
203mm land guns would only be used in specialist artillery units and would only be based on lightened Armata chassis.
EDIT: I think the largest caliber gun we're going to see on a ship could well be the twin 152mm Koalitsiya on the Nakhimov?
Ships have traditionally been fitted with absolutely enormous guns that make the 203mm gun look like a pea shooter because water absorbs recoil very very efficiently.
Older generation guns got bigger and heavier as armour was added to ships... a bit like tanks but on a much more expensive scale, but aircraft bombs and missiles rendered the armour deadweight, so they became light again and so lighter guns were used along with missiles to destroy enemy ships.
The thing is that like the F-35 programme, the Zumwalt class ship with its special guns was a good idea, but the messed it up.
What the US Navy should have done was said to the Army... hey... we want a powerful long range gun we can use instead of expensive missiles and inefficient rockets. Lets work together on a shared gun design, we can make it a standard design... 155mm or 203mm are common for the US Army and Navy... 6 inch and 8 inch guns.... they could get together and develop new ammo, new guns, new propellent, new projectiles etc etc new automatic feed mechanisms etc etc.
Don't expect enormous ranges to start... work in stages... the point is that a 203mm gun is useful for landing force support... and a very long range heavy gun that is accurate is a valuable thing because a 203mm artillery shell that is 110kgs of mostly HE warhead that can be fired to 200km would be an excellent way of dealing with surface vessel threats... even a solid steel shot round round that has no HE that punches a hole right through the front of an enemy ship... a Phalanx would be useless.... most SAMs would be useless because they work by making the warhead explode, but a solid round would just keep coming... it wont do as much damage as a HE round but it will certainly have an effect when it punches a hole deep into the target.
A large ship could carry thousands of shells for sustained support in any weather day or night for landed troops.
An enormous range of shells could be developed including communications jamming rounds to fire into the enemy troop positions so they are cut off from command.
Just gonna leave this excellent article here:
Interesting article, but lots of subtle jabs, like Russian artillery not being constrained by moral rules of engagement when it comes to artillery fire amongst non combatants... suggesting laser guided ammo is not so important for them... ignoring the enormous range of laser guided artillery rounds they have and also use...
And mentioning Bellingcat as a research centre, when in fact they are a propaganda centre.