Changing home page to custom file?

Perhaps you need to review creating a static front page?

However it doesn’t let you choose anything outside of pages.

if using a static front page, possibly with a page template, does not offer enough changes, then consider to create a front-page.php template;

https://codex.www.ads-software.com/Template_Hierarchy
https://codex.www.ads-software.com/Pages#Creating_Your_Own_Page_Templates

I need the homepage to be a new custom file I made for a plugin. If that helps. So instead of doing whatever is in the index.php which loads on default, it needs to display the content of my custom.php file.

I figured this out. Wasn’t sure where I needed the home.php file. Figured out it had to be in the active THEME directory. I was placing it in the root directory.