You are right, I was thinking about a couple I have seen in a pseudo-bridge mode.
On the HH5
DHCP - set to OFF
WiFi - turned off, 2.4 and 5Ghz bands
Set the IP range to the standard 192.168.1.1 to ...256 and leave the HH5 IP address as 192.168.1.254
Then on the connected router, ensure DHCP is on, and the range uses 192.168.0.xxx to ...yyy as appropriate. Yes, a different subnet. If there is a login section set that to OFF.
It may need a little playing with and tweaking, however, it can work.
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