Jerboa is running ahead and already targeting 0.18 API in their 0.0.35-alpha release.
Unfortunately this was not mentioned very prominently (or at least I did miss it) on github.
F-Droid and Playstore still offer previous versions which work with lemmy <0.18.
Since Jerboa itself still needs many updates, I think it would be better to code against the latest stable lemmy release so that many people can use it for testing.
But I'm glad something like Jerboa exists at all, so thanks to the devs for all their work!