I've seen the following thread:
How can I play Minecraft through a proxy server?
But I'm running Linux and I don't have a Minecraft jar file. I only have a binary file that is under the /usr/bin directory that is a standard binary and won't work with Java. How can I proxy Minecraft on Linux?
The new Minecraft launcher is not a Java app on Windows or Linux.
You will have to either use the old launcher (doesn't work with Microsoft Accounts, but I did create a private patch for that), or a launcher that supports proxies like, MultiMC (I know I keep recommending it, but it fixes many problems with Mojang's launcher).
Simply find the proxy option in the settings.
Unfortunately, it doesn't apply to the game. I cannot test this as I don't have a proxy server, but you could try adding the arguments to the game's Java arguments.
