This method works on both MultiMC and PrismLauncher

This method is pretty simple and straightforward!

First you need to create a new instance or using an existing one.

Then you have to click on Edit Instance and go to Settings.

Once you're there, enable the Java Arguments and insert this:

-Dhttp.proxyHost=betacraft.uk -Dhttp.proxyPort=yourport -Djava.util.Arrays.useLegacyMergeSort=true

On yourport you have to put the right Proxy Port that depends from the Minecraft Version you're gonna use, here's the complete list:

• 11701 - From c0.0.13a to c0.0.23a_01

• 11702 - From c0.24_st to a1.1.2_01

• 11703 - For a1.0.8

• 11704 - For b1.3-demo

• 11705 - From a1.2.0-preview to b1.8.1

• 11706 - From b1.9-pre1 to b1.9-pre6

• 11707 - From 1.0.0-rc1 to 1.5.2