Kudos to a Roku Rocks Meta Member Norman, who figured this out:
So give this trick a try the next time the same tooth whitening commercial comes up multiple times during your favorite movie, and you can't stand watching it another single time."Tubi ads—don’t know if anyone knows, but I was doing something and discovered how to bypass the ads. When the ad countdown timer comes on, I pause it around 3-5 seconds. I then skip forward about a minute. I hit play and then immediately skip back to where I originally paused the movie. I hit play, and the movie continues without realizing the ads never played."