@mjg59 The fact it complains even on non-ARC ports suggests that ARC support is communicated over the DDC I2C bus with the EDID data?
So you won't be able to tape it, you'd probably have to use something like this
https://www.lindy.com.au/hdmi-2-0-edid-emulator
(or go full hard and slap your own i2c eeprom on there if you are terminally bored)
@abrasive Yeah that's what I'm worried about, but also that's maybe in the realm of "I can rewrite the EDID if I plug it into a Linux device with HDMI"?
@mjg59 I have an unfortunate feeling that there's all microcontroller and no ROM on DDC nowadays - afaik HDCP negotiation runs over it (along with myriad other things like monitor control on PC-oriented monitors, perhaps some ARC negotiation, etc)