I did not make any changes in FlexQoS configuration, left it as it was installed.
Here's debug output:
FlexQoS v1.1.0 released 2020-12-13
Debug date : 2020-12-18 22:28:26-0600
Router Model : RT-AC68P
Firmware Ver : 386.1_beta1
DPI/Sig Ver : 2.0.1 / 2.208
WAN iface : eth0
tc WAN iface : eth0
IPv6 : dhcp6
Undf Prio : 2
Down Band : 28672
Up Band : 891
***********
Net Control : 1:11
Work-From-Home: 1:13
Gaming : 1:10
Others : 1:17
Web Surfing : 1:15
Streaming : 1:12
File Downloads: 1:16
Game Downloads: 1:14
***********
Downrates : 4300, 1433, 8601, 5734, 1433, 2867, 1433, 2867
Downceils : 28672, 28672, 28672, 28672, 28672, 28672, 28672, 28672
Downbursts : 4800, 3200, 9600, 6400, 3200, 3200, 3200, 3200
DownCbursts : 35200, 35200, 35200, 35200, 35200, 35200, 35200, 35200
DownQuantums : 53750, 17912, 107512, 71675, 17912, 35837, 17912, 35837
***********
Uprates : 133, 44, 89, 178, 44, 89, 44, 267
Upceils : 891, 891, 891, 891, 891, 891, 891, 891
Upbursts : 3200, 3200, 3200, 3200, 3200, 3200, 3200, 3200
UpCbursts : 3200, 3200, 3200, 3200, 3200, 3200, 3200, 3200
UpQuantums : 1662, 1514, 1514, 2225, 1514, 1514, 1514, 3337
***********
iptables settings: <>>udp>>500,4500>>3<>>udp>16384:16415>>>3<>>tcp>>119,563>>5<>>tcp>>80,443>08****>7
-o br0 -p udp -m multiport --sports 500,4500 -j MARK --set-mark 0x8006ffff/0x3fffff
-o eth0 -p udp -m multiport --dports 500,4500 -j MARK --set-mark 0x4006ffff/0x3fffff
-o br0 -p udp -m multiport --sports 500,4500 -j MARK --set-mark 0x8006ffff/0x3fffff
-o eth0 -p udp -m multiport --dports 500,4500 -j MARK --set-mark 0x4006ffff/0x3fffff
-o br0 -p udp -m multiport --dports 16384:16415 -j MARK --set-mark 0x8006ffff/0x3fffff
-o eth0 -p udp -m multiport --sports 16384:16415 -j MARK --set-mark 0x4006ffff/0x3fffff
-o br0 -p udp -m multiport --dports 16384:16415 -j MARK --set-mark 0x8006ffff/0x3fffff
-o eth0 -p udp -m multiport --sports 16384:16415 -j MARK --set-mark 0x4006ffff/0x3fffff
-o br0 -p tcp -m multiport --sports 119,563 -j MARK --set-mark 0x8003ffff/0x3fffff
-o eth0 -p tcp -m multiport --dports 119,563 -j MARK --set-mark 0x4003ffff/0x3fffff
-o br0 -p tcp -m multiport --sports 119,563 -j MARK --set-mark 0x8003ffff/0x3fffff
-o eth0 -p tcp -m multiport --dports 119,563 -j MARK --set-mark 0x4003ffff/0x3fffff
-o br0 -p tcp -m multiport --sports 80,443 -m mark --mark 0x80080000/0xc03f0000 -j MARK --set-mark 0x803fffff/0x3fffff
-o eth0 -p tcp -m multiport --dports 80,443 -m mark --mark 0x40080000/0xc03f0000 -j MARK --set-mark 0x403fffff/0x3fffff
-o br0 -p tcp -m multiport --sports 80,443 -m mark --mark 0x80080000/0xc03f0000 -j MARK --set-mark 0x803fffff/0x3fffff
-o eth0 -p tcp -m multiport --dports 80,443 -m mark --mark 0x40080000/0xc03f0000 -j MARK --set-mark 0x403fffff/0x3fffff
***********
appdb rules: <000000>6<00006B>6<0D0007>5<0D0086>5<0D00A0>5<12003F>4<13****>4<14****>4<1A****>5
filter change dev br0 prio 2 protocol all handle 828::800 u32 flowid 1:17
filter change dev eth0 prio 2 protocol all handle 828::800 u32 flowid 1:17
filter add dev br0 protocol all prio 2 u32 match mark 0x8000006B 0xc03fffff flowid 1:17
filter add dev eth0 protocol all prio 2 u32 match mark 0x4000006B 0xc03fffff flowid 1:17
filter add dev br0 protocol all prio 15 u32 match mark 0x800D0007 0xc03fffff flowid 1:16
filter add dev eth0 protocol all prio 15 u32 match mark 0x400D0007 0xc03fffff flowid 1:16
filter add dev br0 protocol all prio 15 u32 match mark 0x800D0086 0xc03fffff flowid 1:16
filter add dev eth0 protocol all prio 15 u32 match mark 0x400D0086 0xc03fffff flowid 1:16
filter add dev br0 protocol all prio 15 u32 match mark 0x800D00A0 0xc03fffff flowid 1:16
filter add dev eth0 protocol all prio 15 u32 match mark 0x400D00A0 0xc03fffff flowid 1:16
filter add dev br0 protocol all prio 20 u32 match mark 0x8012003F 0xc03fffff flowid 1:15
filter add dev eth0 protocol all prio 20 u32 match mark 0x4012003F 0xc03fffff flowid 1:15
filter change dev br0 prio 22 protocol all handle 802::800 u32 flowid 1:15
filter change dev eth0 prio 22 protocol all handle 802::800 u32 flowid 1:15
filter change dev br0 prio 23 protocol all handle 805::800 u32 flowid 1:15
filter change dev eth0 prio 23 protocol all handle 805::800 u32 flowid 1:15
filter change dev br0 prio 2 protocol all handle 828::802 u32 flowid 1:16
filter change dev eth0 prio 2 protocol all handle 828::802 u32 flowid 1:16
And here's the change of ping at another computer once the phone has started the upload. Increase ~100 times over.
Reply from 8.8.8.8: bytes=32 time=11ms TTL=116
Reply from 8.8.8.8: bytes=32 time=12ms TTL=116
Reply from 8.8.8.8: bytes=32 time=11ms TTL=116
Reply from 8.8.8.8: bytes=32 time=12ms TTL=116
Reply from 8.8.8.8: bytes=32 time=14ms TTL=116
Reply from 8.8.8.8: bytes=32 time=13ms TTL=116
Reply from 8.8.8.8: bytes=32 time=14ms TTL=116
Reply from 8.8.8.8: bytes=32 time=651ms TTL=116
Reply from 8.8.8.8: bytes=32 time=1164ms TTL=116
Reply from 8.8.8.8: bytes=32 time=1437ms TTL=116
Request timed out.
Reply from 8.8.8.8: bytes=32 time=2720ms TTL=116
Reply from 8.8.8.8: bytes=32 time=1617ms TTL=116
Reply from 8.8.8.8: bytes=32 time=758ms TTL=116
Reply from 8.8.8.8: bytes=32 time=837ms TTL=116