Yes it is.
Both knots and core remain compatible with Bitcoin.
There are now multiple client implementations- due to the proposed changes to mempool policy by b-core.
*note:
This mempool change does NOT make the node incompatible with Bitcoin.
Nevertheless, there has been an extreme rejection of this mempool change by users who “run knots”
No one is arguing for a hard fork, the fear mongering suggesting that knots “will” argue for a hard fork in the future is ridiculous and does not represent the intentions of users running knots software today.