Question about old domain redirecting

Hi everybody !

So let’s say I had some content on domain « A » 18 months ago.

A new domain « B » has replaced « A » for branding reasons. And some content from « A » are now on « B ». Some others are deleted and these URL are redirected to « B » home.

Today, « A » is just a webserver with redirections. 0 content, 0 accessible page.

Now that « A » is near completely out of SERP but still have a DR of ~35 I don’t want to miss an opportunity or to mess something up by not doing proper research.

Today I’m asking for a hint !

Is there an opportunity ? What would you do ?

Thanks for reading me