@Frood42 Perhaps I'm missing something, but why not simply configure two separate wifi networks, one for 2.4ghz and one for 5.7/5.8ghz (which is the recommended way for a variety of reasons)
- Since a device will have to have it's wifi network setup regardless, typing in an additional 3 characters (whitespace plus 5G) seems like it should be an acceptable solution
2.4GHz and 5gHz networks do not offer the same throughput, as 2.4gHz network are locked into a maximum throughput of 450mbit/s (with HT), whereas 5.7GHz / 5.8GHz offers a maximum throughput of 866mbit/s+.
- 2.4GHz supports a maximum channel width of 40MHz [HT], whereas 5GHz offers 80MHz / 160MHz [VHT]
Another consideration is does OpenWrt bake in the feature on all routers that prevents a wireless N device from being throttled due to a wireless g or b client connecting? If OpenWrt doesn't, or if this depends on the router, this is yet another reason.
Devices capable of 5.8GHz should be configured at the router level to always utilize the 5.8GHz radio, with the simplest and easiest way to ensure this being to have two separate networks for the 2.4GHz and 5.7/5.8GHz radios.