You can’t mute all servers, though I wish you could, but you can mute each server at a time.

On PC:

1. ⁠Right click the server icon.
2. ⁠“Notification Settings”.
3. ⁠Click “Suppress @everyone and @here”.
4. ⁠Click “Suppress all role mentions”.

On Mobile:

1. ⁠Go to the server or your choice.
2. ⁠Click the ••• at the top of the server near its name.
3. ⁠Press “Notifications”.
4. ⁠Under “Server Notification Settings”, press “Nothing”.
5. ⁠Enable “Suppress @everyone and @here”.
6. ⁠Enable “Suppress all role mentions”.

Do that for every server you’d like to mute. You’ll still get pings when people mention you specifically, but it stops those pesky, often, @everyone & @member pings.