Using clue/ttrss image: https://github.com/clue/docker-ttrss
I was having some problem configuring the container using DB_PASS and DB_USER variables. I ended up using DB_ENV_USER and DB_ENV_PASS and was able to get the container up and running;
docker run -d --name ttrssdb -e 'MYSQL_ROOT_PASSWORD=my-secret-pw' mariadb
sleep 20 && docker run --link ttrssdb:db -p 89:80 -e DB_ENV_USER=root -e DB_ENV_PASS=my-secret-pw -d --name ttrss clue/ttrss