Learning Angular is completely your own choice. But I will advise any beginner React dev to stick to React only and get a better understanding of React first as if you know one framework then switching to other frameworks will not be a challenge. Although, I recommend senior React developers to understand the working of Angular, Vue JS, or any other framework so that they are aware of the internal implementation of all the leading frameworks and how each of them is solving the problem of "rendering complex UI efficiently" in their own way.

Coming to your question about preparing for the interview for a beginner react js developer, I have provided a list of topics that a senior developer looks at while interviewing a candidate.

1. HTML - Learning HTML in depth will allow you to write a well-structured standard webpage
2. Learn about HTML tags, semantic elements, html attributes, custom attributes
3. Why we should use semantic elements?
4. Accessibility - The user should be able to use your application with a keyboard as well ie not restricting the user to use only a mouse or trackpad to navigate or use the website.
5. Best practices for writing HTML structure.
6. CSS - Learning CSS in depth will help in better styling and writing the HTML structure of a webpage.
7. Better learning of CSS will help you in visualizing the design which can be handled via CSS only (without writing extra HTML). Thus, less html code to achieve the desired web design.
8. Understand Specificity in CSS
9. Box Model, pseudo-elements
10. Positioning of elements (relative, absolute, fixed)
11. Making Layout (flex, grid)
12. CSS Modules - component-level CSS so that CSS styles written for a page does not disturb the styling of other pages.
13. Javascript - Till now you can develop a good-looking webpage using HTML and CSS. But Learning javascript will help you in making the website interactive like showing pop-ups on the click of a button etc
14. Javascript basics
15. DOM (Document Object Modal), BOM (Browser Object Modal) - Used to access the HTML structure using javascript, helps to find elements in the tree, access custom attributes or other properties from the elements, updates the HTML elements via javascript (React and all other frameworks provide easy and better ways to perform these actions but internally they efficiently use these javascript core)
16. Execution Context, Different Scopes (lexical and block), Closure, Hoisting, this keyword
17. Callbacks, Promises, Async Await
18. Prototype chaining
19. React - This will help you in maintaining the code structure, writing webpages efficiently, and helping in building a mental modal where you try to look at the webpages into a collection of components and then you create each component one by one to develop the whole webpage.
20. Components
21. Virtual DOM
22. Hooks
23. Usage of "key" in JSX (used while rendering a list)
24. JSX (here your HTML, and CSS knowledge will help)
25. Diff between Client Side rendering and Server Side rendering
26. State Management (either use in built context or learn Redux)
27. React Docs are best to learn React.

These topics can work for 0-4 years of experience candidate. So please learn in depth of these topics depending on your years of experience.

You should have intermediate to advanced knowledge of HTML, CSS, and javascript as using this you can create any website. For Industry, you need to learn React or other frameworks which will help you in developing webpages faster, and efficiently which in turn helps in maintaining the code base.

I have not mentioned any resources rather topics, so that when you google for these topics then you will open 3-4 links to read the topic and then only you can have better understanding of the topic. (Refer MDN docs if not get a satisfied explanation)

PS: I have taken a lot of front-end interviews. Also, I have used Angular, React, and Vue JS in my career to build industry level products.