I've tried Gateron Browns on a number of keyboards at meetups, and on my own testing keyboard.
Gateron Browns are relatively smooth. They are smoother than pre-retooled Cherry MX Browns. The MX Browns for several years leading up to 2016 were very scratchy. Gateron Browns became popular in that time frame, for being cheaper and allegedly better than MX Browns.
After Cherry retooled its browns slightly, some observers have been saying that Cherry retooled its Browns to more resemble Gateron's.
I've heard different things about the 'tactile bump' on Gateron Browns. People say that the Gateron's 'bump' is more distinct. But that hasn't been my experience. The ones I tried on my own keyboard almost felt like linears.
Anyway, Gateron Browns do feel good on a TADA68 (especially with metal case), so try that if you get a chance.
Others have pointed out why Gateron switches are so cheap. Basically, Gateron is part of a new global centre of mass-manufacturing MX switches. They benefit from the lower labour costs and economies of scale in China. I'm sure the Gateron plant is deeply integrated with, or at least proximate to, other areas of keyboard manufacturing in China.
Gateron has been really innovating in the last few years. Chinese manufacturers like Kailh and Gateron are trying to assume leadership of MX switch production, or at least raise their own profile, by filling in all sorts of 'gaps' in the Cherry MX lineup.
For example, Cherry produces the MX Clear heavy tactile, but no light version of that same tactile. That where (Gateron) Zealios come in. They make something similar to the 'Ergo Clear' mod that end-users made, but Cherry never deigned to produce.
Kailh has gone crazy, making all sorts of slight variants. There's Kailh Brown [almost an MX Brown clone], BOX Brown [the Brown concept but on a BOX mechanism] Halo Trues [a heavy semi-tactile], Pro Purples [a lighter Halo True], BOX Burnt Orange, which is just a heavy brown, various 'speed' switches, and so on.
But I like what Gateron is doing. Look at their 'Gateron Yellow' switch, for example. Cherry has a super-light linear (MX Red) and a relatively-heavy linear (MX Black). But nothing in-between. MX Red is too light for many people, and some say it should never have existed. And MX Black is too heavy for comfortable use for many. So why no middle ground after decades of switch production?
In comes the Gateron Yellow. It's affordably priced, along with many of Gateron's 'me-too' switches. It offers something Cherry doesn't (mid-weight linears). And it's incredibly smooth for a stock, unlubed switch.
I'm not a big fan of linears, having only tried MX Blacks and Reds, but I have some Gateron Yellow on the way for testing. And it cost hardly anything to order 50 for a 'testing quantity.'
As they say, innovation occurs at the point of production. Since parts of China are major lower-wage integrated manufacturing hubs, it's easy for them to experiment with concepts. Since they're already set up for mass production, and they have lots of engineers and workers, they can play with ideas and put them into production relatively fast. The penalty for failure and a bad idea is probably lower for Gateron than for Cherry.