Though a paid tool, it is the industry standard for upscaling old footage to 4K/8K. It offers a free trial to test results.

: Go to the Effects & Presets panel and search for "Detail-Preserving Upscale" . Drag it onto your footage layer.

Adding a very fine 1% grain can trick the eye into seeing more detail than is actually there. Why Use 4K Upscaling?

Adobe After Effects includes a native effect called , which is often considered the best "free" way to achieve an Instant 4K look because it doesn't require an external purchase. How to use it:

If you are looking for a direct plugin that lives inside your Effects Panel without spending a dime, here are your best bets.