I have mydomain.com website and need to load this content from newdomain.com. This primary domain change could affect SEO for newdomain.com or will search engine treat it as a standard brand new domain?
I went through this process with my blog, changing from Entrepreneurs-Journey.com, a 10+ year old website with plenty of domain name authority, to my own personal brand domain name - www.yaro.blog.
We did everything by the book, carefully managing the 301 redirects, telling Google about the change, and despite all this my traffic dropped by about 50% after the change.
It did eventually climb back up about 25% more, but even now over a year later it's not back to where it was.
I think the answer is be careful and make sure you are planning to work on your SEO again after you make the domain name change.