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If the end result tastes and drinks like a lager, to an educated palate, then it's a lager. That said, few breweries are making lager without a lager yeast.
Cold fermented kolsch yeast can get you very close as can low temp us05.
The other key processes are temp control during active fermentation to stop ester production, and the ability to hold very low temps for extended periods to clarify and drop out particles.
As for ingredients, lager / Pilsner malt is not essential, but I think you would struggle to make a great one.
Actually I disagree with nearly all of this.
If the end result tastes and drinks like a lager, to an educated palate, then it's a lager.
That's like saying a petrol engine is the same as a diesel, because they both have pistons going up and down. Its wrong, there are commonalities but its the differences that really matter. Apart from the genetic differences Lagers will ferment much colder, will metabolise more sugars than will Ale and manages Sulphur very differently... I could go on but the point is without lager yeast it is not a Lager!
That said, few breweries are making lager without a lager yeast.
I suspect the right answer is NO breweries are making lager without a lager yeast.
Cold fermented kolsch yeast can get you very close as can low temp us05.
Kölsch is easily recognised by its classic fruity flavour, that comes from the Ale yeast used to brew it. Kölsch actually makes a lot of esters if the ferment temperature isn't very tightly controlled. Personally I'm a lot less impressed with US-05 than are a lot of home brewers, it isn't very attenuateive (finishes sweet) and is a pretty poor flocculator (doesn't drop bright), being more attenuateive and dropping bright are two features you really want in a Lager, cant think of two worse choices than Kölsch and US-05, for a clean low flavour beer.
Agree that temperature control is critical to making Lager successfully. As is the right type of yeast, the right pitch rate...
Lager making is a very technical brewing process, it is truly a child of the industrial revolution.
If you want to make lager that tastes great, have a plan, get the right ingredients, be prepared not to rush or cut corners.
As for ingredients, lager / Pilsner malt is not essential, but I think you would struggle to make a great one.
The malt choice is far less critical than you might expect, really the only reason to use Pilsner Malt is for low colour. No problem using most any malt in dark lagers like Vienna, or even at the big black end a RIS, most of which are Lagers.
The OP is a kit brewer, so that's all pretty moot anyway.
Mark