Do you mean a line for White, or for Black? From what I've heard, the Exchange Variation has a simplest Ruy Lopez strategy for White: use the kingside pawn majority to get a passed pawn in the endgame.
simple line vs. ruy lopez for beginners

Mmm, if for Black, maybe the Open Ruy?
p.s.: never heard of Sicilian Kalashnikov, but such a cool name deserves a try!
p.p.s.: I hope a more knowledgeable member gives a comment soon.

If for Black, I've heard that the Berlin Defense (3...Nf6) is typically used as a relatively easy way to draw, which makes sense since the queens get traded off early in some lines, but I'm definitely not very knowledgeable about Ruy Lopez details.
To motivate the discussion more, I've listed Black's main 3rd move options below with my own temporary invented names for variations whose names I haven't seen (and may not exist).
1. e4 e5
2. Nf3 Nc6
3. Bb5 {Ruy Lopez.}
3...a6 {'Stanley Defense.' #1 pop. n 37%.}
3...Nf6 {Berlin Defense. #2 pop. n 38%.}
3...f5 {Schliemann Defense. #3 pop. w 39%.}
3...d6 {Old Steinitz Defense. #4 pop. w 56%.}
3...Bc5 {Classical Defense. #5 pop. w 44%.}
3...Nge7 {Cozio Defense. #6 pop. w 46%.}
3...Nd4 {Bird's Defense. #7 pop. w 49%.}
3...g6 {Fianchetto Defense. #8 pop. n 67%.}

I am still learning opening principles, middle game and endgames. But I have tried the Berlin Defense for the Ruy Lopez and I can say that I feel comfortably with this line. I will keep on my first learning, first things first, as I was advised by several good people in here. But, when I start to chose a opening repertoire, the Berlin Defense will be for sure one of them.

As your name suggests you really do sound deranged. You start off sounding like a 1200 level beginner that says "how can I get the pieces out in a way that I won't get crushed instantly" ...
Then you go off and start sounding like a bit more of an expert... The Kalashnikov Sicilian... the Lasker defense... a hole on d5 ... are you a kid asking how have a safe line to play and learn with, or are you some kind of expert?? Or is there some sort of scam going on here where you are an adult pretending to be a kid? Or a kid pretending to be an adult? Or are there multiple people using the same account name?
What the hell is going on here?

As your name suggests you really do sound deranged. You start off sounding like a 1200 level beginner that says "how can I get the pieces out in a way that I won't get crushed instantly" ...
Then you go off and start sounding like a bit more of an expert... The Kalashnikov Sicilian... the Lasker defense... a hole on d5 ... are you a kid asking how have a safe line to play and learn with, or are you some kind of expert?? Or is there some sort of scam going on here where you are an adult pretending to be a kid? Or a kid pretending to be an adult? Or are there multiple people using the same account name?
What the hell is going on here?
I'm not a complete novice, but I don't like studying openings either (maybe I should start) so I'm looking for simple where I'm not going to die if I don't play the one or two correct moves in a razor sharp theoretical positon. My USCF rating has been in the 1900-1950 range lately. I am an adult, but I also help a lot of the novice players at my local chess club and it would be good to have something to suggest to them as well. Basically something not too theoretical, but also something not to suble; something middle of the road. For example I think the Breyer might be a bit too subtle (plus we might not even see it that often below master level anyway). I am just a little deranged btw.

So are you asking for yourself, or for your "novices" at the club? If you're 1950, you probably already know how to play a Ruy Lopez in a simple non-theoretical way... I still wonder, what the hell is going on here?

you can do this!
1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Be7 5.Qe2
Qe2 is pretty good, and not theoretical
and if black does 3...Nf6, then still 4.Qe2
basically ur just protecting the pawn, and you can still do the regular c3 and d4, and it's pretty good for white
you don't need to know too much

if ur black, then just do 3...Nf6, and don't worry about any theory, because it doesn't matter too much, and your opponent probs won't know anything about it
and u just get a normal game

Thanks for the suggestions so far. One reason this topic interests me is that a lot of novice players are taught to play the Open Game as black, but I rarely see any specific defenses to to the Spanish recommended which is a very complicated opening. This is probably fine for a while since players under expert or master shouldn't be too fixated on openings anyway. Once they do want to learn a bit more about the openings they play though or they get to be a bit stronger it would be nice to have a solid recommendation or two against the Spanish since it's probably the most testing of the Open Games.
@Nicolas I'm basically looking for something that a beginner could play without too much difficulty, but something that will grow with them as a player so that if they were to say reach master level it would still be a good line to use. I'm interested in it for myself as well just to have something simple to play and to be able to teach people the system at the club. Plus, I don't actually know that much theory and I don't really want to learn theory anyway. I suppose a better title for the post would be "simple line vs. ruy lopez for beginners as well as masters".

i mean, u don't need to know a lot of theory for many lines in the closed ruy lopez
because if u don't know theory, u will get a slightly bad position, but not losing, and u can still fight
if it's an open sicilian, a lot of times, not knowing theory means u lose
so don't worry too much about theory
just develop and play safely, and you'll be just a bit worst in the worst case

So are you asking for yourself, or for your "novices" at the club? If you're 1950, you probably already know how to play a Ruy Lopez in a simple non-theoretical way... I still wonder, what the hell is going on here?
Why not just replying his question? I guess it's done now
Roman D’s 2 video series on Steinitz defense is good. Very simple. https://www.chess.com/video/player/ruy-lopez-steinitz-defense---part-1
Anybody have any recommendations for an easy to understand defense to the Ruy Lopez? I like classical openings that give a little space and get the pieces out easily. I'm looking for something that isn't too theoretical, just something that's easy to play, but also something sound that will grow with me as a chess player. I've also thought about switching to the Sicilian Kalashnikov because I like that it has a more rigid pawn structure like a classical opening, but I'm already comfortable playing the Open Games for the most part and I don't know if I would be comfortable with that huge hole on d5. To give an idea of an opening I like my main weapon vs. the Queens Gambit has been to decline it and play the Lasker Defense.