You mean 4GB to open/read/parse that 2.6MB text file? Are you the Discourse developer? A binary executable to read that dump (extracting all the data used by Discourse) and save it to anything else should be imo around 200KB with a, say, 100KB buffer (without bothering with the inclusion of the whole MariaDB for this simple action).
I think it’s not about RAM. The procedure was fast and displayed importing progress for those imported tables. It didn’t “quit”. The users’ table is at the end of the dump, after the topics etc.
I wanted to do this again, experimenting with copying/pasting that users table to the top and perform the same steps from the above manual/page (also with a dump created by phpMyAdmin instead of phpBB), but now Discourse refuses to start the procedure trying to connect remotely although no connection data was added.
I rebuilt the import container, but perhaps something has to be deleted first?