I got the sound working on the seeed ReSpeaker 2-Mics PiHat with this configuration

.asound

pcm.makemono {
    type route
    hint.description "Mono Capture"
    slave.pcm "hw:2"  #For some reason, it came up as Card 2 on a Pi3B+.  I guess on a Zero or maybe a 4 it would come up as Card 1.
    slave.channels 2  #This is the 2-microphone hat
    ttable {
        0.0 1         # Channel 0 outputs to 0 at 100% volume
        1.0 1         # Channel 1 outputs to 0 too at 100% volume
    }
}

pcm.!default {
    type asym
    capture.pcm makemono
    playback.pcm "hw:2,0"  # The speaker is also on Card 2
}

# Do `sudo $(which mycroft-config) edit system` and change the devices to `-Ddefault` to get output working
# Input may just work, but to be sure you can edit `.config/mycroft/mycroft.conf` and `.mycroft/mycroft.conf` and add the following:
#     "listener": {
#         "device_name": "makemono",  #Force the use of makemono
#         "channels": "1"
#     }
# Add the above inside the JSON structure, just below `"max_allowed_core_version": xxx` (where "xxx" is the number) and also terminate
# that line with a comma to get it to read the added code as a separate section.