Where is the TM?
https://www.trademark247.com/trademark.php?mark=blockchain&start=0You can TM the entire domain. "Blockchain" is a common law term these days. It would be very hard to UDRP or sue.
Because of Blockchain.info
Be sure that in this case we are talking about a registered trademark.
100% you will not be able (you or the buyer) to develop a project that has as object of activity: bitcoin/crypto.