In short, WiFi dongle identified as RTL8192EU is killing the 2.4GHz WiFi performance for the entire network! I suspect the reported speed (uplink?) has something to do with it.
[root@ropieee-living ~]# iwconfig
wlan0 IEEE 802.11 ESSID:"Castles Great Hall IoT"
Mode:Managed Frequency:2.447 GHz Access Point: 56:D9:E7:F7:C5:6F
Bit Rate=1 Mb/s Tx-Power=30 dBm
Retry short limit:7 RTS thr=2347 B Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=53/70 Signal level=-57 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:65 Missed beacon:0
[ 4.760743] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
[ 4.891755] usb 1-1.2: New USB device found, idVendor=0bda, idProduct=818b, bcdDevice= 2.00
[ 4.895783] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 4.897844] usb 1-1.2: Product: 802.11n NIC
[ 4.899841] usb 1-1.2: Manufacturer: Realtek
[ 4.901822] usb 1-1.2: SerialNumber: 1CBFCE7BA8A6
[ 10.404467] usb 1-1.2: Vendor: Realtek
[ 10.406640] usb 1-1.2: Product: 802.11n NIC
[ 10.408702] usb 1-1.2: Serial not available.
[ 10.411307] usb 1-1.2: rtl8192eu_parse_efuse: dumping efuse (0x200 bytes):
--- clip ---
[ 10.428066] usb 1-1.2: RTL8192EU rev B (SMIC) 2T2R, TX queues 3, WiFi=1, BT=0, GPS=0, HI PA=0
[ 10.428081] usb 1-1.2: RTL8192EU MAC: 1c:bf:ce:7b:a8:a6
[ 10.428095] usb 1-1.2: rtl8xxxu: Loading firmware rtlwifi/rtl8192eu_nic.bin
[ 10.466817] usb 1-1.2: Firmware revision 19.0 (signature 0x92e1)
[ 11.806556] usbcore: registered new interface driver rtl8xxxu
[ 12.020843] usbcore: registered new interface driver rtl8192eu
The long story, I have two RoPieee (rPi 2), in office and living room, that have been running using a new (to me) USB dongle: (Link to site I purchased) Wireless-N 300Mbps USB WiFi Adapter - HX9500. When I group the two RoPieee they soon studder and Roon reports poor Tidal performance. I initially believed that, but eventually clues in that this was mostly happening when the two RoPieee were grouped and sometimes happened when only one was used and other 2.4 GHz WiFi activity occurred. After turning my UniFi WiFi upside down, including all 2.4GHz devices other than RoPieee, troubleshooting the poor wireless performance I learned that RoPieee was a common denominator in all of this. Without RoPieee wireless performed well! The iwconfig showed the Bit Rate=1 Mb/s which stuck out as iw wlan0 station dump, for example showed much more appropriate bit rates. Replacing the USB WiFi adapter with a couple older ones I have kicking around resolved all of those issues.
Here is info on the working dongles:
The first:
[root@ropieee-living ~]# iwconfig
wlan0 IEEE 802.11 ESSID:"Castles Great Hall IoT"
Mode:Managed Frequency:2.447 GHz Access Point: 56:D9:E7:F7:C5:6F
Bit Rate=65 Mb/s Tx-Power=20 dBm
Retry short long limit:2 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=69/70 Signal level=-41 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:290 Invalid misc:953 Missed beacon:0
[ 4.770661] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
[ 4.918352] usb 1-1.2: New USB device found, idVendor=148f, idProduct=5370, bcdDevice= 1.01
[ 4.923640] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 4.926298] usb 1-1.2: Product: 802.11 n WLAN
[ 4.928844] usb 1-1.2: Manufacturer: Ralink
[ 4.931243] usb 1-1.2: SerialNumber: 1.0
And the second:
[root@ropieee-office ~]# iwconfig
wlx00e04c104778 IEEE 802.11 ESSID:"Castles Great Hall IoT"
Mode:Managed Frequency:2.447 GHz Access Point: 56:D9:E7:F7:C5:6F
Bit Rate=72.2 Mb/s Tx-Power=20 dBm
Retry short limit:7 RTS thr=2347 B Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=70/70 Signal level=10 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:513 Missed beacon:0
[ 4.600003] usb 1-1.2: new high-speed USB device number 4 using dwc_otg
[ 4.731790] usb 1-1.2: New USB device found, idVendor=0bda, idProduct=8176, bcdDevice= 2.00
[ 4.736939] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 4.739622] usb 1-1.2: Product: 802.11n WLAN Adapter
[ 4.742290] usb 1-1.2: Manufacturer: Realtek
[ 4.744862] usb 1-1.2: SerialNumber: 00e04c000001
[ 10.205893] rtl_usb: rx_max_size 15360, rx_urb_num 8, in_ep 1
[ 10.213786] usbcore: registered new interface driver rtl8192cu
I can only assume the the rtl8192eu driver is flaky? Oh, and one RoPieee is running Beta (to use HW volume with IQaudio DAC+) and the other Stable with fixed volume. The information presented on the troublesome dongle is the same, regardless of Beta or Stable version.