Off-page SEO has changed a lot in my opinion. It’s still about links and domains pointing to your domain, but the complexity of how those links are viewed is very different. For example, back in the day, you could get a link from a niche-relevant, high-authority website, and that would help. In my opinion, those days are gone. Google has gotten smarter about links. Does the link bring traffic to your site? This is gold because even if it doesn’t help with ranking, it increases referral traffic, so it’s a win anyway.
Obviously, it needs to be niche-relevant, the link needs to make sense, and it should be helpful to a user. This kind of link matters more than DA, PA, or whatever other metrics SEOs come up with. Traffic is what you want.
Other off-page techniques involve making your brand visible across many platforms. SEOs now call this "Search Everywhere Optimization," but I don’t personally feel this is anything new. In a nutshell, having your brand active on social media, forums, and YouTube, wherever else you can think off... —essentially acting like a big brand — I feel like Google rewards this.