External Monitor crashing MacBook Pro

You have an excellent setup and from what I can see on Amazon reviews, this does generally work with Macs.

There are many possible troubleshooting steps, including switching cables, trying different ports, resetting the power manager, reinstalling macOS, etc. I would encourage you to reach out to Apple Support on this if that's still an option so they can walk you through the various protocols.

UPDATE: I just read a bit further on this and seems this monitor does have significant issues for some users on macOS Catalina, which you are on. You can read those reviews here. It does seem that may be a problem unit. You could still try to reach out to LG or Apple, but you might have to consider returning it. Sorry for the bad news and good luck!

Hey there, more info will likely be needed to help with this:

1. What is the model of the MacBook Pro (go to the Apple menu & select "About This Mac"
2. What version of macOS are you on? (again, "About This Mac)
3. What sort of connection are you using? e.g. HDMI to an adaptor?

Be sure that whatever version of macOS you are on, that it's up to date by checking in Apple menu>System Preferences>Software Updates. Do be careful, however, to first upDATE and not necessarily upGRADE if you are not on macOS Big Sur. The latter can look like an update, but is a full fledged OS upgrade. There are a lot of changes in Big Sur and if you are not already on it, you may lose functionality with incompatible software. Updates, however, should be largely safe to do.

If you are using one type of connection, try the other option e.g. if you're using HDMI to USB C, try USB C direct.

That's quite a nice, high end monitor. If you just purchased it, you should be able to look to LG for support. Depending on the age of your Mac, you may also still have AppleCare.

Good luck!