I have a Pixel 2, so still have a notification LED. But if we assume the AOD options are the same in the more recent devices without one:
Firstly, the actual lock screen isn't the problem: it can show as much notification information as you want there (how much is shown depends on what you choose, e.g. if I tell my SMS app to hide sensitive content it shows less than if I don't). But you have to wake the screen to see the lock screen. Actually since I normally wake the screen with my fingerprint, i.e. unlock at the same time, I rarely see the lock screen at all.
So the real problem is what you see when the screen is off. And for that the only built-in option is the AOD, which is crap. If you turn it on you get the time, the date in small font, and then a set of tiny icons to show which apps currently have notifications. You can set it so that when a new notification comes in it shows more information for a short time, but then it will revert to what I described above. And there is no option to turn off the clock and date and just have it show when there are notifications (though as I have a couple of permanent notifications that wouldn't be much use to me anyway). Personally I turned the AOD off a long time ago: if it had the option to only show notifications, plus the ability to choose what apps can/can't show notifications on the AOD, then it would have some utility: if you saw anything on there you'd know something had arrived, though it's still less visible, especially at a distance, than a notification LED. But having to count the dim little icons at the bottom of the AOD to see whether there is anything new is of such limited utility that I'm almost surprised that Google think this is useful - "almost" because I long ago got over being surprised by Google making myopic choices.
So that's it for built-in options, unless there are more options on later devices which lack the notification LED (which, to be honest, I doubt. Google assume you use the AOD, and why not provide any other options in the Pixel 2 as well?).
The real question is whether there are third-party options that can be used to provide the functionality you want? Unfortunately as I have an older Pixel which still has a notification LED I've never investigated this.