Can LN clog main chain BTC? Main chain BTC can handle something about 300k tx per day without increasing fees, open and closing channels need to be done using standard tx on main chain. So the question is if we will have large world adoption, can LN can produce 300k tx per day (sum of opening and closing txs)?
The answer is yes, but not anytime soon.  Also, it's a function of how frequently channels are opened and closed, which can be estimated, but is not "really" predictable.

If you read the LN whitepaper [link], it mentions in the conclusion that "to enable 7 billion people to make two channels per year with unlimited transactions inside the channel, it would require 133 MB blocks"