@Rem3
In the Asus router, try enabling n/ac/ax under the 5ghz "wireless mode" settings. (looks like you may have ax-only enabled).
The Roku Ultra you are showing is wifi5(ac) capable/compatible. (cannot see or connect to an (ax) network.
Only the newest Roku Ultra 4850 is currently wifi6(ax) capable.
Additionally, only (ax) devices can use WPA3 (security protocol for wifi passwords), so make sure you have WPA2 enabled as well so that your n/ac devices can recognize and connect to your wireless network.
Roku Community Streaming Expert
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