If anybody has @types/styled-components-react-native installed and still gets the error maybe it helps the trick as described at https://github.com/styled-components/styled-components/issues/2370. For me it helped to add the types to tsconfig.json file:

{
  "extends": "some/tsconfig.base",
  "compilerOptions": {
    // ...
    "types": [
      "jest",
      "cypress",
      "@testing-library/cypress",
      "@types/styled-components-react-native"
    ]
  },
  // ...
}

Add the styled component type for react native by installing

npm install @types/styled-components-react-native
// or 
yarn add @types/styled-components-react-native

For configuration details, you can read their guideline.

Don't set DefaultTheme in your themes/index.ts. It's already used and is just an empty object.

Update your themes/index.ts to this:

import { colors } from "./colors";
import { sizes } from "./sizes";
import { spacing, lineHeights } from "./spacing";

const theme = {
  colors,
  sizes,
  spacing,
  lineHeights,
};

export default theme;

Update your types/theme.d.ts this:

import "styled-components"
import theme from "./src/themes";

type ThemeInterface = typeof theme

declare module "styled-components" {
    // eslint-disable-next-line @typescript-eslint/no-empty-interface (this is only necessary if you ur eslint complains. Since it should be and Interface and not a Type.) 
    interface DefaultTheme extends ThemeInterface {}
}

And you should be gucci.