Ignoring Wired Headset detection - Not working on Android 6.0

This works on my Nexus 5 with Lollipop, and stopped working since android M developer preview 1. SoundAbout will report routing to speaker, earpiece, etc, but no sound comes out. Forced routing to speaker or earpiece does not work. Speakerphone works normally on phone calls regardless of SA status. I'm currently running Android 6.0 with SA 2.6.5.7 beta. With 2.6.5.6 beta, short ~75ms blasts of music would come through the speaker at the beginning of a Hangouts dialer call - to date the only sign that SA is working in any way. Bluetooth routing works fine in all cases, with or without SA.

My headset port is damaged (exposed to 48V phantom power from a soundboard), so the phone thinks a headset is permanently connected. To date SA is the only solution that works.

Does anyone else have this issue with Android M/Marshmallow?

Thank you for this excellent software!

There was a mistake in 2.6.5.7.

Try this latest Beta instead.
https://soundabout.forumotion.com/f8-download-beta-versions

I wiped SA program data/cache, uninstalled 2.6.5.7 and installed 2.6.5.8 beta. No change in behavior

If you drag down and watch the status bar, at the top of the screen, does the SoundAbout notification message keep changing the audio output status rapidly?

I'm wondering if the damaged headset port is sending signals very rapidly?

Thanks, there is no such behavior and I have never seen that happen.
My SA configuration is default, except I have "Wired Headset detection" unchecked in connectable devices>Wired headset settings. In that case, the notification message is "Phone speaker for media".
If I check "Wired Headset detection", then the notification is "Wired headphones for media". And with the mic sub-option, "Wired Headset (with mic)..."
If I explicitly state an output path in SA on the main screen, the notification will correctly state the path, but will not work for media or phone calls. Speaker phone works fine, as do notifications and ringtones thru the speaker. Bluetooth routing works fine. If I have SA routing specified, or headset ignored, I will get a short ~100ms snippet of the phone audio through the speaker when ending the call. Hangouts has no speakerphone option currently, so SA is working for a very short time, at the calls end.
As I mentioned in the OP, this is new behavior in Marshmallow - SA always worked in L. I will make a nandroid, and attempt this under lollipop to confirm it still works there. However, since speakerphone does work in a normal call, I suspect this is a new function of M that is interfering.
Thanks so much!