Is the "decapsulate" function from lattice based cryptography homomorphic?
Kyber claims to be CCA secure. CCA schemes cannot be homomorphic (thinking through this may be a useful exercise).

It may be useful to try to work through this particular example with pen and paper by looking at algorithm 5 in the Kyber paper. Note that what is returned is some hash, which you should not expect to have homomorphic properties.