> Reading this HN post on the Chevy Volt it's starting to look to me like the general approach of installing a 50ohm "silencing antenna" could end up working for a lot of different cars out there. I'll certainly be giving it a try on my GR Corolla now so I can get the microphone back while still keeping the DCM disabled.
I started researching this again because of this, and it looks like you may need to watch out for "Dark Draws" (https://www.reddit.com/r/subaru/comments/1bn1c3a/dcm_bulleti...) where the DCM trains the battery because it couldn't make a connection. Apparently this has been a problem with some 3G based units when they shut 3G down.
It looks like Subaru, at least, has made a replacement DCM "bypass" box to allow the DCM to be removed without disabling other car features: https://static.nhtsa.gov/odi/tsbs/2024/MC-10251102-0001.pdf