I'm going to assume it means that the client (installed app) is moving so fast (and breaking compatibility so fast) that some servers are currently unable (or don't want) to keep up. A reason to hold versions is, for example, to have more stability assurances.
The Lemmy ecosystem is going to be a mess for the next months until everything is properly oiled.
Sort of. If I understand correctly something in 18 broke captcha so they can't use it without being swarmed by bots. It will supposedly be repaired with server version 18.1. The Connect app for Lemmy doesn't seem to have an issue with the older server version if people want to give that a try. Jerboa is broken with lemmy.world currently.
0.18 is the latest version of Lemmy. It has some issues with SPAM prevention. Most are waiting for 0.18.1 to release, bringing back some SPAM prevention tools. The app is developed by the same developers as Lemmy and they released some features that require 0.18 in the app.
If it's possible you could rollback to an older version of the app until the sites you subscribe to update.
The warning is somewhat confusing. Second paragraph should say something like log into an instance that has updated to the latest version. You can always see the instance version at the bottom of the page when using a desktop browser.
Looks like the recent update is is around half adopted across all the instances based on what I've seen. Some instance admins are holding out for the 0.18.1 version where captchas will be reinstated.
Captchas had to be disabled for the 0.18.0 transition from web sockets to http. The migration away from web sockets improves client performance quite a bit and obviously it's essential for Jeroba.
Interesting the app and website tell you the website is not on the latest version. That’s good for both the user and site owners to keep the software updated. It like everyone said, lemmy took away some admin and captcha settings with the last upgrade. Many server admins are waiting for them to be restored.