I take it you don’t have a router that allows multiple SSIDs per band.
In other words, you could advertise SSID “foo” on both bands but advertise SSID “foo-low” only on 2.4 GHz - and then configure the Librem 5 to use “foo-low” and leave all your other devices on “foo”.
Or see next.
Yes. See the earlier discussion: Traveling Experiences - #20 by irvinewade