I think there are two different things to say about this here.
In this topic and version 1.41.7, the Agents weren’t removed but rather stopped functioning (you could still see them in the “Legacy Agents” view in the Server settings). But when you added a new library item, metadata wouldn’t be downloaded and added to the item and “match” and “fix match” search results were empty.
Rolling back to 1.41.6 seems to fix the issue. As stated in the second reply, this seems to be a bug because the “old” metadata agents aren’t a priority as of now.
As for legacy agents in general, well, they have been removed (on the Nvidia Shield with 1.41) and should be removed on other Platforms as well at some point.
Plex has stated that they are working on an alternative but it isn’t clear what that alternative will look like or functions. But from what I gathered, it won’t be a 1:1 system, so you won’t be able to just keep using those old agents in the new system anymore. As for the NFO importers. IIRC they did say that they want to add NFO support in the official Plex Agents. This would mean that you don’t necessarily need a 3rd party agent for that but could just use the official Agents.
This is based on the Fireside chat from last year.
