The newest trailer for Pokemon: Let’s Go! Pikachu and Pokemon: Let’s Go! Eevee revealed a replacement for HMs and ride Pokemon, along with additional exclusive moves for both partner Pokemon, Pikachu and Eevee.
Specifically, new “Secret Techniques,” will replace the original HMs and the more recent Ride Pokemon system. Much like HMs, Secret Techniques grant Pokemon the ability to overcome obstacles to help you get around.
Chop Down cuts down trees in your way, Sea Skim lets you surf on water, and Sky Dash replaces Fly as a form of fast travel between cities. Sky Dash might look a little familiar for fans of Pokemon Yellow and the TCG – it involves using colorful balloons to fly away, like the ones attached to Flying Pikachu.
Source: IGN.com HMs in Pokemon Let's Go Replaced by Secret Techniques