Not a solution that works or is available to everyone, but for me, small doses of marijuana taken just before bed has changed my world.
I’m currently traveling and in a state where that isn’t an option and I haven’t had more then 4 hours in each of the past few nights. Will be glad to get some rest tomorrow.
I (unfortunately) am sometimes exposed to second hand marijuana smoke (from other people in the building smoking) and it does seem like there might be some positive effect in my case (there are a bunch of different types and I have no idea which ones I've been exposed to). A major negative is that marijuana is usually grown with heavy pesticide use (even the certified organic stuff) so unless you grow it yourself it isn't really healthy. Of course, smoking anything is also not healthy but you don't need to smoke it (and shouldn't). Also, many things help with sleep short term but with long term use you go back to normal (except that often quitting makes things worse for a while).
I've also had bad insomnia most of my life (and a non-24 hour circadian rhythm starting somewhat over a decade later). Early on it seemed to be anxiety/racing thoughts related and what finally mostly prevented that part for me was meditation. I still occasionally stay awake due to racing thoughts but not often. Unfortunately, that didn't ultimately help with the insomnia, which got somewhat worse (or at least different) over time :(.
The meditation method I used goes like this:
1) In general, althernate between focusing your attention on your breath as it touches your skin above your mouth (since it does that all the time you can kind of feel it and not feel it at the same time) and either active or passive muscle relaxation (mostly active unless you are getting tired enough not to feel like it).
2) For active relaxation, tense muscles in one group a time (I doubt the exact organization matters, I think I used three or four groups: arms and hands, core muscles, legs, and possibly feet) for several seconds and then feel the contrasting relaxation for a while after you release them. For passive, just tell yourself you are relaxing those particular muscles and try to feel them relax.
3) The time split between focusing on your breath and relaxing muscles doesn't matter, if you are having trouble focusing on your breath then just switch to a relaxation cycle.
4) For getting to sleep, wandering thoughts are fine. What you want to avoid is strong emotional reactions to your thoughts, including a feedback loops such as where something feels like an excitingly good idea (when you are half asleep and not so good at evaluating what is a good idea) and that leads to other thoughts that feel like good ideas or building on the same idea. If you really thing something is a good idea get out of bed and write it down along with enough follow up throughts to find the same stream of thought the next day (should it prove interesting to do so, which is not usually the case in my experience). Otherwise go back to the relaxation/breath cycle when you notice you have a stronger emotional reaction to your thoughts. Other feedback loops include remembering past mistakes or bad events (which can either then go to moment by moment recall of one event or remind you of other similarish situations) and focusing on a difficult current situation (again either going into detail about the current situation or often recalling any memory connected to anyone or anything involved in the situation). It may (or may not) be helpful to think of it as a type of internal drug addiction and you are trying to recognize when drugs that keep you awake are released internally rather than noticing particular thoughts.
5) Visualization can make it easier get to sleep if you are able to do it, so you can try imagining yourself on a warm beach as you do the breath focus and relaxation. I can usually only do that when I am about to get to sleep, if I happen to think of it (and noticing I'm about to get to sleep can make it harder to actually get to sleep :( ). Also, make sure you are actually sufficiently warm (and not too warm if you can avoid it) since that can sometimes be surprisingly difficult to notice even if it is keeping you awake.
6) I didn't become a world class meditator over the decades I've had insomnia, I mostly just try to use it when I notice racing thoughts, which is not that often these days (infrequent enough to not always think of it when it does happen :( ). I think it was 5-10 years that I meditated frequently before racing thoughts were rarely an issue, although it was very quickly obvious that it was helping. I've lately been thinking that I should try it again more regularly to see if it could help some even without racing thoughts (however, I don't think the circadian issue is affected much if at all by the meditation).
Some people find a formal Cognative Behavioral Therapy course to be helpful (or reading books that cover the same techniques), however some of the techniques won't work at all if you have circadian issues (and could make the circadian issues worse).
I’m currently traveling and in a state where that isn’t an option and I haven’t had more then 4 hours in each of the past few nights. Will be glad to get some rest tomorrow.