Temporal.io is a pure code solution. I haven’t written a system with it yet, but @salaboy and I had a long Twitter discussion with some advocates and the founder. It seems like the big difference is that with Zeebe you get BPMN, which means your cross-org conversation has an artefact that never goes out of date and that everyone in the business can understand.
The counter-argument was that coders don’t like BPMN (I get it - who wants to go from writing parameterized reducers to drawing pictures, amirite?).
Of course, if you have stakeholders who don’t speak code, then this means you aren’t making diagrams in Confluence that are out of date before you even finish them (the situation that lead me to Zeebe - solution: “we’re going to run this system off the diagrams in Confluence using the BPMN plugin!”)