Error "Operation too slow" when the launcher downloads files

/!\: The version of the launcher is 2.1.5410, downloaded from the official's Minecraft website, which isn't available from the JIRA list of versions

On a fresh installation, when clicking "Play", the launcher starts downloading the client (Currently 1.14.4).

It fails with this error message:

Failed to download file.
Name: 1.14.4.jar
URL: https://launcher.mojang.com/v1/objects/8c325a0c5bd674dd747d6ebaa4c791fd363ad8a9/client.jar
Error details: Operation too slow. Less than 30 bytes/sec transferred the last 60 seconds
Filename on disk: 7238-d030-c3fc-6584
Path: /tmp/7238-d030-c3fc-6584
Exists: File

Downloading this file manually with curl worked, in less than 2 minutes (And now it blocks on fastutil-8.2.1.jar).

I have a 2663 kb/s download bandwidth (As announced by the modem) and the connection is likely unstable. It is very unlikely that it dropped under 30 B/s for 60 seconds long, though.

The filesystem where the launcher is downloading files (/tmp) is of tmpfs type, have a size of 4GB and a used space of 4%. Thus, it's unlikely I'm hitting a disk I/O throughput or space limit.