No. And let me elaborate.
If it were any other “typical” puzzle, like a wooden puzzle box or a jigsaw puzzle, yes, it would be cheating to find the solution on the internet. (Though, for the jigsaw puzzle, you wouldn’t usually check the internet; you would just look at the photo of the finished puzzle on the box and start working … likely from the edges or corners!) But a Rubik’s cube is not your typical puzzle!
Typical puzzles have only one solution and as soon as you know it, a puzzle is done and dusted (though, you can still have lots of fun solving it again and again). But Rubik’s cube doesn’t have just one solution. Every time you scramble a cube, you get a (slightly) different puzzle with a slightly different solution. Mathematically, a 3x3x3 Rubik’s cube has 43,252,003,274,489,856,000 (that’s 43 QUINTILLION) different combinations and solutions! And when you learn how to solve the RC on the internet, you don’t learn one solution. (That would be cheating!) No. You learn the method to solve any possible combination which is just like learning the rules and strategies of a boardgame or a sport.
Over the past few decades, solving Rubik’s cube has indeed become a proper sport where “professionals” compete (to solve it in the shortest amount of time), where people come up techniques and strategies (for example, the “beginner” vs “speed-solving” algorithms), where companies come up with innovative equipment (speed-cubes, touch-timers etc), and where variation of original sport develop over time (look up “blindfold Rubik’s solving”, “Rubik’s cube solving while juggling 3 of them” and such).
In summary, no, learning online to solve Rubik’s cube is not cheating at all … as long as you learn the generic method of solving it. If you were to learn to solve the specific scramble patterns on your cube, that would be cheating. But it won’t do you much good too because the next time you lay your hand on the cube, it might be one of the other 43,252,003,274,489,855,999 scrambled states, leaving you quite clueless how to solve it!