Anyone have experience with using de-esser for sibilance in home audio system?

I would be surprised if there is anything wrong with your ears. Does the issue happen with every song that you hear or only with some of the songs?

As far as the de-esser is concerned it could possibly help, as could a parametric e.q. Most de-essers now days are plug-ins so you would need a DAW to be able to use one. The couple of outboard de-essrs that I’m aware of require a special rack to mount them in.

but I do hear it through earbuds.

This is a problem.

Do you only hear it when a "S" or "SH" is enunciated, or do you hear it thru the entire vocal track?

Does it sound like a very high pitched hissing sound or more like a high pitched ringing sound?

You say that you hear the sibilance issue when using ear buds, so that eliminates the room as an issue. Sounds like you have at least two systems maybe three depending on where the ear buds are used. Assuming the gear for each system is unique to those systems, I think it would be highly unlikely that a different component in each system would develop the same issue at the same time, so though we cannot 100% rule out the gear I think the odds for the gear being the problem are very very slim. If you have tinnitus I would think that you would be hearing the hissing sound constantly all day long and if you are not, I doubt that is the problem. It could be that you have developed a sensitivity to high frequencies and this should have shown up in your hearing test and your audiologist should have discussed this with you if you were outside of the standard deviation for that portion of the spectrum. Also I think you would hear overabundance of sibilance when watching television and in conversations in general. As far as the reverse, where the sibilance region is normal and everything else is deficient, this too should have shown up in your hearing test and your audiologist would probably be recommending hearing aids, not to mention that the whole world would be sounding rather thin and tinny.

Is it possible to listen with other people to see if they hear the same issue? That would at least tell you if it was a gear or source material issue.