I've had sciatica and the best sources I found was to get relief through pressure points. If the muscle is in spasm around the sciatic nerve, you need to release that spasm to relieve the pain. I've had deep muscle massage that has helped. Stretching the piriformis will help. The one that worked for me was to lie on a tennis ball at the pressure point. It released the spasm within minutes.
If your problem is not muscular, then most of those remedies won't work. My back has now gone to degenerative disk disease and stenosis. My pain isn't when I sit, but when I stand. So, it is probably different than yours.
I go to a chiropractor, but chose wisely. I went to one that liked to twist and turn. It made the problem worse. PT didn't help. Inversion works somewhat, but isn't a cure all. Walking seems to help loosen things up for the day. I try to get a couple of miles in during the morning.
I do use CBD oil. I also find gummies work and are convenient, especially when you're on the go. It doesn't do away with pain, but helps to control it. Read up on it before you get into it. There is no standard dose. You'll have to figure that out on your own. Find a reputable manufacturer, and there are lots of them. Cost depends on strength. The downside is CBD is not long lasting.
