The MathMesh crypto platform (refs at the bottom) is a newly-proposed technology stack which has been somewhat cheekily called a "Grand Unified Theory of Security on the Internet". Its "Meta Cryptography" module relies on the following property of Discrete-log Diffie-Hellman:
$privKey: x, pubKey: X = x.P$
$privKey: y, pubKey: Y = y.P$
Therefore you can derive "combination keys" by either combining two public keys or two private keys.
$Z=X \oplus Y = (x \otimes y).P$
for some appropriate definition of $\oplus$ and $\otimes$.
Will this survive the transition to post-quantum asymmetric KEMs? More specifically, how likely is it that there is some definition of $\oplus$ and $\otimes$ that allows "combining" of public keys and private keys in this way for lattice, code, multivariate and/or SIKE keys?