I use Mumble (desktop client) + Murmur (as LAN server) + Plumble (Android/iOS client). This results in the lowest latency I've ever achieved (sounds almost like normal loopback, theoretically 7ms WiFi delay + 2x 10ms codec delay = 27 ms).

For the latest version, see github.com/pzmarzly/mic_over_mumble.

Fragments of README (rev 8c827fe)

1. Install Mumble (desktop client) + Murmur (server) + Plumble (Android/iOS client). Set all 3 programs to use best quality and minimal latency. Set mobile client to always streaming.

2. To install Mumble + Murmur on Ubuntu, you can use:

   sudo apt install mumble mumble-server
   sudo systemctl stop mumble-server.service
   sudo systemctl disable mumble-server.service
   

3. Copy mic_over_mumble anywhere - it will use ~/.mic_over_Mumble as configuration directory.

4. Run mic_over_mumble. It will start the server on LAN, then start Mumble (if asked for nickname, enter anything other than SuperUser). Then connect your mobile device to the LAN server manually. Please note that Mumble mobile app has some issues.

5. Then, set up your programs to use either "Monitor_of_Mumble" or "VirtualMic" as input device (they are linked). E.g. in OBS:

   

Copy of mic_over_mumble script (rev 8c827fe)

#!/bin/bash
set -euo pipefail
# PAID = PulseAudio ID
# ID = PID / process ID

function main () {
    if [ ! -e ~/.mic_over_Mumble ]; then
        mkdir ~/.mic_over_Mumble
    fi
    cd ~/.mic_over_Mumble

    rm murmur.ini || true
    echo "bonjour=true" >> murmur.ini
    echo "bandwidth=130000" >> murmur.ini

    if [ ! -e ./initdone ]; then
        echo "You will need to configure Mumble client to use the lowest possible latency."
        echo "We will start Mumble now. Please complete setup wizard and go to settings to increase quality and decrease latency."
        echo "Also, mute your microphone (if you have one) in Mumble."
        echo "Then close Mumble."
        run_mumble_client_wizard
        touch ./initdone
    fi

    echo "Starting Mumble server (murmurd)..."
    run_mumble_server_bg
    sleep 5
    echo "Starting Mumble client..."
    MUMBLE_CLIENT_ID=$(run_mumble_client_bg)
    sleep 15
    echo "Fetching PulseAudio configuration..."
    MUMBLE_CLIENT_PAID=$(get_mumble_client_paid)

    echo "Changing PulseAudio configuration..."
    echo "Adding sink..."
    SINK_MODULE_PAID=$(add_sink)
    sleep 3

    echo "Fetching current configuration to redirect Mumble..."
    SINK_PAID=$(get_sink_paid)
    pacmd move-sink-input "$MUMBLE_CLIENT_PAID" "$SINK_PAID"

    echo "Adding a virtual microphone..."
    SOURCE_MODULE_PAID=$(add_source)

    echo "Done. Please use pavucontrol to ensure everything works."
    echo "Press Return to shut down..."
    read -n1 -s -r
    echo "Shutting down..."

    echo "Stopping Mumble client..."
    kill -KILL "$MUMBLE_CLIENT_ID" || true
    sleep 2
    echo "Stopping Mumble server..."
    # TODO: find a better way to kill murmurd
    # (it forks, so we cannot use its PID)
    pkill murmurd || true
    echo "Restoring PulseAudio configuration..."
    pactl unload-module "$SOURCE_MODULE_PAID"
    pactl unload-module "$SINK_MODULE_PAID"
}

function run_mumble_client_wizard () {
    mumble >/dev/null 2>&1
}

function run_mumble_client_bg () {
    MUMBLE_URL="mumble://localhost"
    mumble $MUMBLE_URL >/dev/null 2>&1 &
    echo $!
}

function run_mumble_server_bg () {
    murmurd -ini ./murmur.ini &
    # echo $!
    # TODO: here we can get murmur's PID
    # (uncomment the line above)
}

function get_mumble_client_paid () {
    pacmd list-sink-inputs |
        grep -F -e "index: " -e "media.name = " |
        cut_every_second_newline |
        grep -F -e "Mumble" |
        print_second_column
}

function add_sink () {
    pactl load-module \
        module-null-sink \
        sink_name=Loopback_of_Mumble \
        sink_properties=device.description=Loopback_of_Mumble
}

function add_source () {
    pactl load-module \
        module-virtual-source \
        source_name=VirtualMic \
        master=Loopback_of_Mumble.monitor \
        source_properties=device.description=VirtualMic
}

function get_sink_paid () {
    pacmd list-sinks |
        grep -F -e "index: " -e "name: " |
        cut_every_second_newline |
        grep -F -e "Loopback" |
        print_second_column
}

# https://serverfault.com/a/375098/449626
function cut_every_second_newline () {
    awk 'ORS=NR%2?" ":"\n"'
}

function print_second_column () {
    awk '{print $2}'
}

main

Android File Transfer for Linux will always work! it just works!

see answer here: https://askubuntu.com/a/1111802/183131