The Minecraft launcher keeps logs of game events as they happen which can be useful for debugging errors or other issues that may occur within the game. Follow the directions below to obtain these log files from Minecraft.
Open the Minecraft launcher if not already open. Click on ‘Settings’ button.
Turn on the options Keep the launcher open while the game is running and Open output log when the game starts by clicking on the grey check boxes.
The check boxes should now be green. Click on the Java Edition tab on the Launcher and start the game now by clicking on PLAY.
This windows should appear - for now let it run in the background.
As soon as your issue has occurred, copy the entire log by pressing Cmd-A (Windows / Linux) / Cmd-A (Mac). All text in the window should be highlighted. Afterwards press Ctrl-C (Windows / Linux) / Cmd-C (Mac) to copy the text into the clipboard.
Open Ubuntu Pastebin: https://paste.ubuntu.com
Paste the text you copied from the file into the text area in the center of the page at Ubuntu Paste by pressing Cmd-V (Windows / Linux) / Cmd-V (Mac), or by right-clicking on the Content text field (highlighted in red), then select Paste. The “Poster” field will be your Minecraft Username.
Press the “Paste!” option and it will redirect you to a URL with all the text you pasted. The URL looks like this: https://paste.ubuntu.com/p/AbcDefg1h3/
Copy the URL as seen in the image below and give it to the person that is asking for your Launcher log.