Since our cats arrived a year and some months ago, we tried a few of the cat litter options available from our local supermarket (supermarché). They ranged in price, from expensive to very expensive, and effectiveness. In the end, we decided the costlier option lasted longer and retained more smell, so was better value for money.
That was until Her Outdoors had Another Great Idea.
I don't know where it came from - maybe because cutting our own wood creates a lot of sawdust, or that we use sawdust in the chicken house, or that we'll be using sawdust in our compost toilets - but I can tell you what it is: Sawdust.
We’ve litter-tested the concept for long enough now to announce that it is by far the cheapest and most effective non-product not on the market. Our cats have absolutely no problem with it (we introduced the sawdust little by little over a few days before going completely litter-free). And it is 100% compostable (although we’re composting it separately for a while before feeding it to plants).
There's probably a gag here about reducing litter, but I'll leave you to look for it.