A funeral can be a religious ceremony.
It can also be a spiritual ceremony or a secular ceremony.
It can also be a mixture of the above, and it often is.
It can be whatever you want it to be.
If, for example, you have a crematorium booked for a funeral, you can ask the funeral director for a funeral celebrant to conduct the ceremony.
The funeral celebrant can accommodate your wishes and design a bespoke funeral ceremony that has meaning for you.