Found this on another forum:

The Qualcomm Atheros QCA9565 802.11b/g/n WiFi Adapter is a single band wifi card that only works on the 2.4 GHz wireless band.

Anytime you see a wifi N card where the suffix ends in b/g/n, that means it is a single band (2.4 GHz) card only.

Qualcomm Atheros QCA9565 WiFi is B/G/N which means 2.4Ghz only.

This is not correct re: b/g/n meaning single band only.  There were 5ghz standards prior to AC, so some adapters listed as N spec are dual band--just not AC dual band.  N600, N750, N900 routers were routers that were dual band but not AC dual band.

Inspiron 15 3567 hardly a year old. Why is it still 802.11bgn? Can this be replaced by a 802.11ac adapter? My download speed is only 40 mbps whereas my other PC is 160 mbps.

I don't know what the Qualcomm QCA9565 looks like but can it be replaced with Intel Dual Band Wireless-AC 7265 802.11ac available on Amazon for less than $15 and is it easy for a non-techie to install?

I looked at the service manual. It's too much trouble to pry open the keyboard, remove a dozen screws, then flip it over and remove another dozen screws before you can get to the adapter. So I ordered a 1200Mbps 802.11AC NANO USB Wifi Dongle on ebay for less than 10 bucks. Once I plug it in I'll just disable the Qualcomm adapter. I'm surprised Dell still puts in 11 b/g/n adapters on 2019 laptops.

This type of router cannot connect to a 5 GHz network.

@Quirky Dude I'm with you on this one I have a inspiron 24 all in one 3455, with the qualcomm qca9565 802.11b/g/n network card and it use to connect to my 5g network no problem and now it will not even show the 5g networks in the network list.  Makes no since. 

Same issue here.

I bought a brand new Dell Inspiron 3671 back in December.

No 5 GHz, only 2.4.

My thought is that since 5 GHz has limited range compared to 2.4, and there is no external or "aimable" antenna, that Dell and Qualcomm are avoiding a support issue by not providing 5 GHz.

I'm quite tempted to buy an internal NIC with an external antenna. Very good ones can be had for $50 or less.

update: The wifi dongle kept disconnecting so I put in an Intel 802.11ac adapter and now get 360 mbps.

So, did you check this site https://bestparentalcontrolapps.com/highster-mobile/ to fix an issue with spy app or..?

@tlewers​ same here. not crazy. I have the same inspiron 24 all in one and I DID used to connect to 5g. I wonder if they disabled in in a driver update.