Here is another issue, not mine however trying to help someone out. has limited mechanic skills.
It goes clunk when pedalling forward only in the small ring. And not every rotation. Claims it is a new groupset.
Here are my thoughts.
Rear derailleur is straight?
Check the wear on your chain.
Could be index of front derralieur if its only in small.
Check bottom bracket. Although probably not.
Taking off wheel and putting back on common to have to tweak the indexing.
Take the bike off. Spin the fly wheel fwds and see if it makes same sound.
Wear difference in small ring vs big ring. new rings required.
Possibly worn/wrong speed quick link. Try replacing it either way. I had something very similar (clunk you could hear and also feel through the pedals) which was solved by using a new quick link
I know this is a late addition to the thread, but just wanted to chime in that I’ve had my Kickr Core since mid-2019 and love it. But the bike I had on it was an older 9-speed and when I went to give it a bath the other day, realized the rear jockey wheels were totally shot. And you can’t buy any 9-speed rear derauilleur stuff, so decided to use my gravel bike for now. I had a spare new 11-speed cassette on the trainer and when I put the gravel bike on… GRINDING! Didn’t think my google fu would be good enough to find a solution but I did… here. Putting the cassette on from the bike itself and it was much smoother. I should have thought of this myself, because any time in the past I went with new cassette it was because the chain was worn and I replaced both but didn’t here.
So glad that I found this thread !!