How to do:

1. Make sure you dont have any cached server recourcepack files
2. Join a server (i tested with manacube)
3. While the pack is downloading, press esc before it finishes
4. Use the keys on your keyboard to leave the game (up arrow, enter)
5. Repeat esc then up arrow then enter a few times (it may be unneccasary)

What will happen:

• Your game will get stuck on the mojang loading screen
• If you join a singleplayer or multiplayer game, the recourcepack wont load or it will load the manacube pack if you tested with manacube (only got this to happen once and i wasnt recording)
• Nothing will happen, try again

Things you may have to do

• Join a server like cubecraft and leave until you get the ratelimiter
• Not repeat the keys so many times (or at all)
• Memorize the keys to join another minecraft server and do that after repeating it

Link to the video (sorry it 15 minutes long the part showing the getting stuck on loading screen is at about 2:19 - 3:11 but you can watch the whole video if you want) https://drive.google.com/file/d/1v-94eMfXxFOj4rUgJ37ZR8ixBaj0spzl/view?usp=sharing