So I actually have this monitor, though I don't have a M1 Macbook. I used it with an eGPU setup with a 2018 13" Macbook Pro over a year ago, and I discovered that the LG Monitor failed to communicate to MacOS or something, and MacOS subsequently was unable to detect it and generate the right .plist file for it.
Anyways, for missing resolutions, maybe this fix will work ?
Last year I was able to figure out a fix where you could generate the correct .plist file using a .plist generator webtool someone had made, and I don't know if it applies to the m1 Macs specifically, and also have no idea if this is the exact thing people are having issues with here, but if someone wants to try it's worth a shot. I ended up stumbling on this MacRumors thread because I have an M1 Air on order and this monitor is already sitting on my desk. Not gonna lie, kinda upsetting to see this monitor is still so problematic (haven't used it for the past 9 months) and was hoping it was slated to be a smooth experience after it's been out for this long.
I documented my fix here:
https://egpu.io/forums/postid/58536/
Keep in mind this was an issue I resolved over a year ago, I don't know if this is still a problem that exists or if this is the problem that you guys are all experiencing. I guess I wouldn't be surprised if that's the missing piece people are having here, but it'd be disappointing that LG/Apple haven't resolved it after this long. You'll also have to reapply this fix every time you do a MacOS update.
If no one is able to give this a shot, my M1 Air arrives this Friday and I'll give it a go and report back.
Wake issues:
Unfortunately, one thing I can add is that this monitor has always had wake up issues all the way back to when I used Mojave. It has to be something on LG's end that either isn't solvable via firmware update or they're simply unwilling to solve it. I don't think Apple is the entire reason, if any reason at all, that this monitor has had such interoperability issues with MacOS.