Finding a deterministic way to split a secret into 6 shards

I'm looking for the best deterministic approach to split a secret into 6 pieces. No Shamir Secret Sharing Scheme, please. The goal is to be able to rebuild the original secret using any 2 of those pieces.

The best is still the Slip39 mnemonic shares. It is available on wallet like Electrum and Trezor hardware wallet.

Please forgive my ignorance, but what's wrong with SSS and what do you mean by "*deterministic*"?

I'm assuming you're more concerned with having multiple entities hold shares of a secret, and in the context of Bitcoin to sign transactions. SLIP39 which is an implementation of SSS is a good one, though it has never been formalized into a Bitcoin standard. Blakley's scheme is another form of secret sharing, though I prefer Shamir's, partly because of SLIP39's existence and also that it doesn't offer additional benefits. As far as information-theoric secure, I believe these are the two main ones. Recently, there's a scheme called Multi-Party Computation as well. If you're going with that then might as well use Multi-sig since the latter is formalized into a standard.

I believe he means the output is always same. AFAIK some SSS tool (such as https://iancoleman.io/shamir/) would generate different output if you use exactly same input on different occasion.

Is deterministic Secret Sharing Scheme even possible? As far as I know these algorithms rely on randomness and if their randomness is "guessable" they lose their purpose.

Then the solution is simply to use non-random inputs, though as pooya87 pointed out, that would introduce weaknesses.