> > In fact, for reasons I’m yet to discern, my iBook’s internal AirPort Wi-Fi card can’t connect to modern Wi-Fi networks—they simply confound it.
there's a huge number of 802.11b and 802.11g devices that simply won't operate at all on a 2.4 GHz radio of a 802.11n/11ac/11ax network that is set to "dual 40/20MHz" channel mode. And definitely not on a 40 MHz channel. Remember that in older wifi systems there was no such thing as a 40 MHz channel.
same thing for old 802.11a 5 GHz band devices, they don't understand anything other than a fixed 20 MHz channel.
And that's before you run into problems with modern usage of WPA2.
there's a huge number of 802.11b and 802.11g devices that simply won't operate at all on a 2.4 GHz radio of a 802.11n/11ac/11ax network that is set to "dual 40/20MHz" channel mode. And definitely not on a 40 MHz channel. Remember that in older wifi systems there was no such thing as a 40 MHz channel.
same thing for old 802.11a 5 GHz band devices, they don't understand anything other than a fixed 20 MHz channel.
And that's before you run into problems with modern usage of WPA2.