Yep, your latter statement is correct. There is no single adapter I can carry around with my laptop (with a HDMI cable and expect it to reliably work with whatever HDMI device the location happens to have.
Note that it ends saying "The Good News: DisplayPort Works
I purchased a couple of USB-C to DisplayPort adapters from Monoprice and am pleased to report that they both work just fine. As hoped, these simple adapters natively and passively attach Alternate Mode DisplayPort from the MacBook Pro’s integrated AMD GPU through the Intel Thunderbolt controller and connect perfectly with the monitors I’ve tried."
I then Googled "active displayport hdmi converter" (to find one with a little chip inside, that actively really outputs true HDMI.)
Which says "Connect an HDMI® monitor to a DisplayPort® Video Source".
Since it's active, the Mac should see it as a DisplayPort device. The device then takes that signal and outputs HDMI. So while the resolution might not be perfect, I would expect this combination to work and let you connect your Mac to any HDMI device, period.
Since it sounds like you have this problem a lot, if you did end up buying that device I'd be keen to know if it worked! (email in my profile.)
http://blog.fosketts.net/2016/11/26/beware-usb-c-hdmi-adapte...
Note that it ends saying "The Good News: DisplayPort Works
I purchased a couple of USB-C to DisplayPort adapters from Monoprice and am pleased to report that they both work just fine. As hoped, these simple adapters natively and passively attach Alternate Mode DisplayPort from the MacBook Pro’s integrated AMD GPU through the Intel Thunderbolt controller and connect perfectly with the monitors I’ve tried."
I then Googled "active displayport hdmi converter" (to find one with a little chip inside, that actively really outputs true HDMI.)
I found this page:
https://www.startech.com/eu/m/AV/Displayport-Converters/Disp...
Which says "Connect an HDMI® monitor to a DisplayPort® Video Source".
Since it's active, the Mac should see it as a DisplayPort device. The device then takes that signal and outputs HDMI. So while the resolution might not be perfect, I would expect this combination to work and let you connect your Mac to any HDMI device, period.
Since it sounds like you have this problem a lot, if you did end up buying that device I'd be keen to know if it worked! (email in my profile.)
Thanks.