So, I spent the better part of the day trying to track down this noise on my wife’s car. If I gently rock the car side to side, I can replicate this knocking/thud. Found that if I hold the spring or down lower on the sway bar, while rocking I can actually feel it as it knocks on the passenger side. Actually, holding the sway bar on either side (passenger and driver’s) I can feel the knock but with my ear, I can only seem to place it on the passenger. Have a ‘21 SE with approx 5k miles. Going to try and get into dealer, but unsure what it could be. Sounds like 3 different things based on this thread.
Now, the weird/funny part is that when taking the cowl cover off, I found a cut plug just laying there on the strut tower under the “vent”. Also, when I took the fender liner off on one side (side closest to door) I could see some sticky liquid that looked like spilled coffee. This is not on the actual strut, but back on the sheet metal and plastic liner. I‘m sure this didn’t happen, but I swear the first thing that popped in my mind is that some guy on the line accidentally cut the plug and spilled his coffee at the same time. Rather than clean it up, just said “**** with it, no one will notice ...” and slapped the fender on.