As the title says, How can I add a custom CSS to all posts without affecting homepage CSS on WordPress?

And I know that some plugins like "WP Add Custom CSS" would work for this and I am actually using it, and it does work but, what I want to do is give all my posts the same exact code, I don't want to give every post manually the same code over and over.

Because if I wanted to change this code later on, then I will have to go back and edit every post that I made with this new code change.

For example, I have this CSS code:

.post-meta { margin-right: 0px !important; }

Every post needs to have this code but without affecting homepage CSS.

As the title says, How can I add a custom CSS to all posts without affecting homepage CSS on WordPress?

And I know that some plugins like "WP Add Custom CSS" would work for this and I am actually using it, and it does work but, what I want to do is give all my posts the same exact code, I don't want to give every post manually the same code over and over.

Because if I wanted to change this code later on, then I will have to go back and edit every post that I made with this new code change.

For example, I have this CSS code:

.post-meta {
    margin-right: 0px !important;
}

Every post needs to have this code but without affecting homepage CSS.