Use MacBook as microphone for iPhone?
I have ReSound made-for-iPhone HAs. ReSound sell a device called a "multi mic" and also a "mini mic" which is a remote microphone which will transmit direct to the HAs. It also has a 3.5mm jack so can be plugged into a computer (or TV) and the computer sound is sent straight to my HAs. Speaker is cut off. I keep a dedicated multi mic permanently connected to my computer. To hear computer sound streamed to my HAs I just have to change to the correct streaming source on my phone. Works brilliantly and has had a lot of extra use with Zoom meetings.
I would be amazed if Starkey don't make a similar device.
I would add that the multi mic is extremely useful in many other situations.