I'd combine with the following:
1) citations. Work great to create authority and relevancy at the same time, plus they look more natural.
2) PBNs. Relevancy. Get a good PBN (PRIVATE) going and you'll see decent results within 2+ weeks. Some good providers as well, but as soon as it's selling publically, there's a way higher risk for a deindex in my opinion.
3) Press releases. They don't work as good as before, but still do for me.
4) Social signals. A solid fundamental touch with lots of (good) socials will definitely help ranking.