Though by 1880 small arms like the Lebel rifle could be made from steel, to handle the greater pressures of smokeless powder, making stronger cannon- especially big cannon-was a far greater technical challenge. It's hard to say how the gun in the video was constructed, but likely it was made with a cast iron tube or steel tube that had wrought iron bands or coils shrunk around it, to keep it from bursting-

Hence, in England, we had reason to congratulate ourselves on the certainty and cheapness of manufacture of wrought iron coils, as long as moderate charges of comparatively quick burning powder were employed, and as long as adherence to a muzzle-loading system permitted the projectiles to move away at an early period of the combustion of the charge. Then the pressures, though sharp, were of short duration, and were not thoroughly transmitted through the body of the gun, so that the solidity, mass, and compression of the surrounding coils proved usually sufficient to support the interior lining.

Maitland, 1882 Modern Ordnance

As Maitland noted, though, smokeless powder required much more strength- it can be three times the pressure of black powder- and that iron-wrapped cannon would perhaps not stand the strain. He also noted that, as smokeless powder is a propellant and burns much more slowly than black powder ( especially if it's made in large grains) , there is a real benefit to having a very long barrel- with a constant generation of gas keeping up the pressure, the shell can then be accelerated to the very end of the barrel and so given a higher velocity. Long barrels are harder to load from the muzzle- so breech-loading became necessary. Which meant a breech mechanism strong enough to hold the pressure, also, and capable of sealing off the explosive gas ( which, at around 30,000 psi, can do more than stain clothes.) A barrel and sealing breech mechanism able to take higher pressure are things the Krupp company managed to accomplish around 1880, with the British engineer Armstrong not far behind..but though apparently smokeless powder cannon were used in the Russo-Turkish War of 1878 ( I don't have a clear reference right here) big coastal defense guns like the one in your video would be still muzzle-loading and black powder fueled in the 1880's, until the beginning of the introduction of more modern ones like the 13.5 inch smokeless breechloading guns by 1889.

TL:DR the cannon was limited to black powder: by 1905 there were better , breechloading cannon.