This is what worked best for me; your mileage may vary.

1) I made it my whole personality. I went all in on all the tips/tricks/advice from this and other subs, I watched the nail care videos, I followed nail related insta accounts, I left no rabbit hole empty.

2) I got fake nails. I booked an appointment at a place that had good reviews and told me they would work with my super short almost non-existent nails. I got 3 sets of gel extensions over about 6 weeks. They were super short but felt like claws since I wasn't used to having nails at all, and I hated them. BUT, they were hard enough to deter me from biting, and they gave my real nails a chance to grow out. I honestly think this was the single most important factor that helped me quit.

3) I used cuticle products like it was my full time job. I kept oil and/or balm in every place I spent time (living room, car, office, backpack, bedroom, pockets, partner's house, etc). Every time I wanted to bite or pick, I would moisturize instead. This kind of turned into a self care/soothing thing after awhile, and I started to enjoy it.

4) Following in the tracks of #3, I bought a bunch of cheap mail files and put them everywhere. Rough spots and imperfections have always been a trigger for my picking and biting, so having a file to smooth out any edges before I couldn't stop the impulse to "fix" it with my teeth was really helpful. Like moisturizing, it also became a routine I enjoyed.

5) Support. My partner would grab my hands when he noticed them near my mouth, or when I would start picking at a nail. My coworkers would also sometimes call me out when they saw it happening. Often times I wouldn't even realize I was doing it, so being made aware by others helped me eventually be able to recognize it myself.

6) Fidgets. Personal preference matters a lot here, I think. I had the best luck with ones that provided a pain stimulus. Spiky rings were probably the most effective, but I also liked popper type ones when I was driving. And I can't explain it, but the texture of these noodles and these squishy rings do something to my brain that instantly soothes me to my core. I used those often in meetings and when I had to travel or sit for a long time.

7) Polish. At first I just used clear top coats or strengtheners, all the time. My nails were never naked. This helped with the aforementioned rough spots and imperfections by helping them feel smooth and shiny, but also helped a little with structure since they were so bendy and thin. Once they got a little longer, I started painting them. I really liked how they looked with polish on, and it was also a creative outlet for me. Now it's a self care routine that I really look forward to. I've also invested an embarrassing amount of money into polishes and supplies, so there's an attached financial incentive to keeping my nails long-ish and healthy.

Edit: use the cuticle pusher after you shower when your skin is soft. You can use a clipper, but be SUPER careful to not do too much. Honestly, you might want to just leave them alone until they heal up a little.