Easily the best and most significant sonic tweak one could ever make!

@sokogear. Agree not a tweak, that was a creative way in doing my part to get a majority of the members to click on the post!

The sound quality of hearing aids are hindered mostly by the poor performance of the little microphones. I find that if I insert the earpieces gently, the domes allow more sound to enter with proper phasing from my speakers for a more natural presentation

An earlier response suggested blowing the nose before listening.   As you've probably experienced when changing altitudes, such as when flying, changes in the inner ear pressure can dramatically affect hearing.  If you are prone to nasal congestion due to allergies or whatever, as I am, making an effort to pop the ears (equalize the inner ear pressure with the pressure outside the ear) can spare you from assuming your system has gotten out of sync.  More than once I've tweaked when I didn't need to, but now know better.
If you live in a state where it's legal, consider trying a small dose of edible THC and see what it does for your hearing.  I retired from the service after 28 years and stayed away from that stuff.  Not worth loss of a pension!  A little careful experimentation since retiring determined that a tiny dose (2.5 mg) of THC made my hearing feel like I remember it from my childhood.  It was like a $100K upgrade to my system.  My neurologist had no plausible medical explanation.  I'm in my mid 70s and I suspect that over time, my brain has made some maladaptions that prevent me from hearing as clearly as my ears are physically capable of performing.  My audiograms are quite good for age with equal roll off at the highest test frequencies, but no low or mid losses.  The golden lining for me was that in finding that my hearing was more intact than I thought, I was apparently able to "retrain" my brain to hear the missing sound qualities without the need for being stoned.  Perhaps some support for my amateur theory is that friends with true degenerative hearing loss find no audio benefit from the THC.  I'm in the medical profession and on the conservative end of the scale when it comes to drug use.  I'm somewhat hesitant to put this out there but thought it was worth any flak I get for it if any of you are fortunate enough to have the same experience I did. Great listening sure helps with pandemic isolation.  One further suggestion - DO NOT try to tune your system when you are under the influence.

Costco is now carrying the Phonak aids under the Kirkland Signature name.  The latest one is the 9.0T Premium.  This has full Bluetooth using both android and apple phones. The app lets you add programs, with control over three frequency bands, noise suppression, and amplification. Also control compression, and directionality of the microphones at different parts of the behind the ear electronics module. 
As i write this I am currently streaming directly to the hearing aids from Tidal.  In this mode the frequency balance is not great, and I do not see a way to modify it.  Normally I would not stream directly to the hearing aid, but use a "music" setting and listen to my system through my GoldenEar speakers.
The hearing aids are very effective when making  a phone call - the sound comes from the streaming direct to the hearing aids and is very clear - the phone mic picks up your voice.   Of course, you can also stream the audio from a football game and no one else will notice...
It certainly helps my enjoyment of music!
Only $1499.99 at Costco, and Medicare will reimburse for most of the expense as far as I understand. 
If only it would cure the tinnitus...

@aural_grat--or try to tune a guitar when fully under the influence !  But i've got news for you--on 2.5 mg you are still "stoned"--only just enough for the music, but not enough to be stupefied.  As i'm sure you know being in the profession, today's medical grade is way more potent than most of the ragweed back in the 70's--Enjoy the upgrade !