If you want to get quality backlinks, you do not have that many options.
I used to buy crowd links. Crowd links are quite powerful, but only when this technique is applied the right way and combined with other link-building techniques.
If you want to read more about this SEO technique, I'd recommend checking out this article: https://telegra.ph/Crowd-marketing-The-most-natural--effective-link-building-technique-12-24.
Also, if you wish to read more about link building, make sure you check out this article: https://www.acuteblog.com/2022/03/20/link-building-basics/.