Now that Nintendo has effectively announced the end of the Nintendo Creators Program (which will happen by the end of the year), it means that if you wanted to upload videos of yourself playing a Nintendo game and monetize it on YouTube, you can go ahead and do so without worrying about Nintendo crashing your party (within reason, of course).
With Super Smash Bros. Ultimate having just been released, we imagine that there are many out there who would love to upload their replays to share with the internet, and the good news is that Nintendo has announced that in an upcoming update to the game, replays will be converted into videos which means that not only can you keep those replays from being affected by balance changes, but you will also be able to upload them to the internet easily for others to watch.
At the moment how the replays are being saved is that it records the timing and order of button presses. The problem with this particular method is that when a balance update is released, that punch that was supposed to do more damage is nerfed, which means that the logs are messed up and that the replay is no longer as accurate.
However with the upcoming update, those replays can be converted to videos which means that you get to keep that replay as it was, regardless of balancing changes. This update is expected to arrive in the next few days and will bump your version of the game up to version 1.2.0.