sorry i am making another comment, but do you think this set up would work:
Sony ECMCS3 > 1/8 extension > TRRS adaptor > Android phone
I am asking because we might be able to get someone to donate the Sony ECMCS3 and adaptor, so we would only need to spend around $15-20 to buy the extension
Found a solution. The Sennheiser cable is proprietary (has different pin setup to your usual mic cable) so you need to get an adapter before connecting it to the USB Type-C adapter.
Pictured below is the adapter that I purchased and connected to the Sennheiser cable and then to the USB Type-C adapter; everything works fine now:
Working Sennheiser lav mic with Note 20 Ultra
[Edit: OUT OF STOCK LINK] Adaptor: SC4 TRS to TRRS Mic Adapter, Ancable 3.5mm TRS Female to TRRS Male Short Converter Connector Compatible with iPhone, Android Smartphone, Tablets, Rode SC4 Cable, Rode VideoMic, VideoMic Go, BOYA Mic
[Edit: NEW PRODUCT LINK] https://www.amazon.com/dp/B01N9CJDVE/
Here's the cheapest solution I would try. I had the opposite issue with my audio interface and plugging my headset that had a mic channel into the interface.
This adapter would remove the "headphone" band on the plug which can cause interference.
It’s just a trs to trrs adapter, right? If so, there are several that a search will show, such as:
And
