Most Lemmy instances are on v0.17.4 but the latest version of Jerboa expects v0.18 which is the pre-release version. I suggest you downgrade back to Jerboa v0.0.34 from github for now.
The version 0.33 of Lemmy should still be compatible. You may be able to get it working directly fron the github releases or from a store allowing older versions like f-droid.
However, it would be expected that most instances update to 0.18 soon. It may take some time tho.
Yes today a new backend version will be released. You have to wait that your instance (lemmy.world in this case) updates the backend. Lemmy.ml is already updated