Can't create nor start existing

Reading the "light" HELP documentation, I tried to create a new project on Ubuntu 20.04. It writes the file and folders locally then stops. Opening the file result in an alert "Could not load the document" (not super precise message):

Trying to connect to local postgres running as container is declined because of "Internal error" (should tell more), on postgres 12.5:

Trying to connect to distant postgres server is declined (postgres 12.5). Starting glom from terminal results in: gi.repository Python Module Not Installed

gi.repository? Is it still existant in 2021?

Can someone provide a simple but complete tutorial about creating a new project with specs about the local server (version?) and settings? Bonus: What Glom UI interface creation looks like? Does it export to something? A few screeshots are welcome :)

Forgot to say, I can access my Postgres servers fine with ERDesignerNG so it's not a postgres issue.

Have a nice day