Can I use Apple Card credit if I do not own an iPhone?

You can, but you will be limited to purchases at an Apple Store and at the online Apple Store only.

click here ➜ How to apply for Apple Card - Apple Support

If you apply online and don't add Apple Card to an eligible iPhone or iPad that you own, you can only use it to make eligible purchases online and in-store at Apple.

Yes, go into an Apple Retail Store and apply online for an Apple line of credit. You will not be applying for an Apple Card Mastercard account, but rather a line of credit available for purchase of Apple products in Apple Retail Stores and also online at Apple.com/store.

You must have an eligible device, typically an iPhone, to apply for Apple Card Mastercard account.

How to apply for Apple Card - Apple Support