@khungus: Here are two options that may help.
1. Turn on HDMI-CEC in the AVR if you haven't already. This usually keeps the HDMI circuit in the AVR "on" when the AVR is turned off. HDMI-CEC can however, cause other issues like automatic input switching, devices turning on by themselves, etc which you may not want to happen. This does also draw a few Watts of additional power when the AVR is off.
2. Some AVRs have an "HDMI Passthrough" or similar option which allows audio to pass to the TV when the AVR is off. Try that? Again, this may draw a couple of Watts.
One of these may help the STB remember the UHD setting, but no guarantees.
Anyone solve this issue of the 4k receiver not remembering the UHD setting? Each time I turn the 4k receiver on it has defaulted to 720P and I have to chnage the setting to UHD manually.
Thanks for the tip - will try to look for similar on my Denon tonight and cross my fingers, since I have the same model as user gp-se ... will report.