When i tried to install misago docker on my rpi i got
I cannot reproduce this locally with latest
Our docker file contains this part that adds postgresql-client to installed packages:
wget -q https://www.postgresql.org/media/keys/ACCC4CF8.asc -O - | apt-key add - && \ sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ buster-pgdg main" >> /etc/apt/sources.list.d/pgdg.list'
Your error looks like this code didn't work for you. I'll try setup test forum on digital ocean next to see if I can repro this issue there.