As of snapshot 20w07a, I experience the following on my Linux machine: if a hopper switches from being enabled to being non-enabled or vice versa, this is not immediately visible in F3.

Steps to reproduce:

1. Create a new superflat "redstone ready" creative mode world with no structures enabled
2. Give yourself a hopper and a redstone block
3. Place the hopper and look at it with F3, note that it shows as enabled
4. Place the redstone block adjacent to the hopper

Expected result: the hopper now shows as not-enabled in F3.

Actual result: the hopper now shows as enabled in F3.

When you right-click the hopper to inspect its contents, then the hopper's state shows correctly in F3. Then you can destroy the redstone block and get a similar result, but obviously the other way around.

The hopper does seem to actually switch states correctly, by the way - there doesn't seem to be a bug there. It looks like it's purely in the way F3 shows the hopper's state.

I'd note what Java version I'm running but I seem to have a couple of JDKs on my system and I have no idea how to know which one is the right one. Please let me know if you'd like me to figure that out.