I've never actually tried this, so it's a bit of guesswork. I only thought of it after I had my displays set up [& don't want to mess anything up now;)
First, switch off anything that claims to be "smart" or "self-adjusting" in the display's controls. I've never used an LG monitor, but their TVs have so much "user-friendly" going on they're a nightmare.
Use the built-in Display Calibrator Assistant - but do it without modifying anything other than the external display's own controls; so the profile you get at the end doesn't interplay [you can discard it once you're done].
System Prefs > Display > Colour
Hold Opt as you click Calibrate… & you get more options once you check 'Expert Mode'
Going into this mode disables any existing profile, so if you see that it looks odd on any already-calibrated monitor, ignore that for now.
You may only be able to do anything useful with the first screen, the brightness/contrast, & the last couple, for gamma & white point, but it might put you in the ballpark before you run the colorimeter over it.
Of course, as soon as you leave this Assistant, the system will re-apply your existing profile - but you can ignore that too, as you're about to replace it with a calibrated one.
This may not really gain you anything, as it will be the first step once you run the X-Rite calibrator, but it might just reduce time needed to get settled values. I always tend to run my calibration a few time to make sure it 'feels' the same each time. I've known things to wander on occasion. If you have the option in the X-Rite app - I know there are different parts licensed for different 'spending' on X-Rite - but if you can get to it use the large colour patch 480 or so colours, not the simple 118 patch version. It is considerably better.
Further thoughts - depending on your intended usage & the actual capability of the display, you may need to set the hardware to P3, ProRes, Adobe RGB or sRBG before doing this basic brightness/contrast. I'd be very wary of P3 or ProRes, because I doubt the ColorMunki can handle it. Stick to Adobe or sRGB, especially if you are working to web.
When I first set mine up I experimented to see which felt more portable across to other managed displays [just in case I was fooling myself] & ended up with Adobe RGB, as the screens handle it well, that's what my camera likes, & it also seem to handle export to sRGB nicely.
Late edit, after comments.
It apears the latest ColorMunki is the same hardware as the i1Display Pro, only the software is different. Mine was the older hockey-puck model, marketed as ColorMunki Smile. In which case it would be worth extracting the most out of it by giving DisplayCAL a try as well as X-Rite's own calibration software.