This is actually something we're actively working on! Nhat Pham is working on a patch series called "virtual swap space" (https://lwn.net/Articles/1059201/) which decouples zswap from its backing store entirely. The goal is to consolidate on a single implementation with proper MM integration rather than maintaining two systems with very different failure modes. It should be out in the next few months, hopefully.

> Would be nice if zswap could be configured to have no backing cache

You can technically get this behavior today using /dev/ram0 as a swap device, but it's very awkward and almost certainly a bad idea.

Very much agreed. I feel like distros still regularly get this wrong (as evidence, Ubuntu, PopOS and Fedora all have fairly different swap configs from each other).