Allow me to clarify, I wrote that before coffee and work:
Most of these cheap forges are very bad design. This one takes it to the extremes. Not enough interior volume means uneven heat and a highly oxidizing atmosphere. Adding more burners in an attempt to even out the heat means even more oxidizing. The designer just looking to make money of off Forged in Fire and not actually studying forge design means you're getting ripped off from the beginning.
Good forges are designed to heat via radiant heat from the lining, not direct blast from the burner(s). This is the fundamental problem with ALL of these cheap forges with burners of widely variable quality entering at top dead center. For a very few applications where you don't care about decarburization, material loss to scale, or can mitigate these effect by very fast heats, this can work. The only two examples I can think of where this isn't a problem are bending horseshoes and spot-heating when making armour.
That's where this design came from, travelling farriers who needed a lightweight, fast-heating forge so they can bend and fit shoes from barstock in the field. This does not in any way translate to bladesmithing, where our main concern is a neutral to reducing atmosphere and minimal oxide scale.
The second fallacy is more burners = better/hotter forge, especially for knife work. We've covered it here a lot, but it always bears repeating: At only one time while making a knife do you want the whole thing at heat, and that's during heat treatment. You can only forge about a hand's-breadth of steel per heat. Any heating you do beyond that is wasted fuel, grain growth, and decarburization. Even when forging swords, you do so a hand's-breadth at a time. Even with solid fuel forges, for all of history the ones made for actual forging as opposed to heat treating are managed to have a hot zone of no larger than could be forged in one heat. Admittedly, the factory forges where they made anvils were a lot bigger so they could get anvil-sized blocks of iron and steel to uniform welding heat, but the average bladesmith/cutler's forge only heats enough steel to hammer by hand in one heat.
The other part of that observation is that people seem to think they can just turn off one or more burners of a multi-burner forge to get shorter heats. On these cheap ones that doesn't work, again because the chamber is too small for efficient radiant heat transfer.
All this is why, back in the day (by which I mean the revival of the hand-forged blade in the USA from the later 1970s into the late 1990s) Don Fogg, among others, developed the vertical blown forge. The only commercially available forges at the time were coal forges or Mankel-type open-sided gas forges designed for farriers. NC tool used the basic farrier design and made it better by enclosing it more, and using more ceramic fiber than castable refractory for lighter weight with shorter heat-up times. Big industrial forges like Johnsons were all-brick behemoths that used blown burners and wasted most of the heat you put in them. What Don and the other did was take the blown burner idea and combine it with the lightweight shell that NC Tool used, modifying the interior to be round and for the flame to enter at a tangent to the lining rather than like a blowtorch in a bottle. This swirling flame resulted in a far more even heat with far less oxidation. By then standing the cylindrical shell on end with the burner entering near the bottom, you get a truly even, reducing atmosphere perfect for welding or forging blades. For whatever reason, even today the only way to get a forge like this is to make it yourself. The better commercial gas forges like Chile Forge, Diamondback, Majestic, and so on do sometimes use an angled burner entry that moves the hot spot to the wall rather than the center of the floor, but no commercial forge I know of uses true tangential burner entry and none use the vertical design.
This is why I like the Mr. Volcano in the cheap forge category. It has an angled burner so you can still use the hot spot if you want (and it can be handy sometimes), and it has a large enough interior volume to allow good radiant heat transfer. You do need to use the bricks as partial doors, but that's not hard. The burner is the best part of these, though. Some cheap forge burners like the Vevor and especially the Devil Forge, can't be adjusted enough to offer anything but a highly oxidizing flame. The Mr. Volcano is close to a T-Rex Hybrid Burner in the level of adjustability, and it has a properly tapered burner flare unlike any of the other cheap units.
All of that said, in my own shop I mostly forge in coal, because it what I learned on and because for axes and tomahawks it's easier to fit awkward and large shapes into the heat compared to a typical gas forge. When I do use gas, it's a very small forge made from a pair of hollowed-out soft firebricks with a venturi burner of the type sold at www.hightemptools.com. I have forged a sword with that little thing and its 10-cm hot spot. It is capable of welding heat, but is limited to small billets less than 2.5 cm square and 8 to 10 cm long.