After using template I had to remove port from MAUTIC_DB_HOST, since I was getting Unknown server host 'mysql.railway.internal:3306'
After this change, all worked fine.

Ohh sure, let me check it out.

Working without changing port for me, can you share some more details. I'll try to fix it asap. Thanks for letting me know :)

I am sorry, it was an error in the other Mautic template, not yours.
I have another problem, though, that I can't figure out, as I am lacking knowledge of both Mautic and Docker.
On every redeploy, I am redirected to the Mautic installation. I am guessing it is because of missing local.php? I tried adding additional ENV variables like MAUTIC_DB_DRIVER (setting it is supposed to make Mautic assume it is installed), but not sure if it is the right way to solve that.