Yes, it's due to removing Websocket in v. 0.18. It's supposed to be fixed in 0.18.1. I'm also on Lemmy.world and haven't had too many issues on the latest version of Jerboa but they recommend using the previous version or a different app for the time being. That said, for the main reason we're getting so many Reddit refugees being an issue with third-party apps, particularly on mobile, pushing an update to the official app here that requires a site version not all the main instances are on board with isn't a good PR look.
0.18 was a big change (for example websockets to http), I'd imagine future versions are unlikely to be so drastic and will allow Jerboa to be compatible with older versions