If you want to replicate the Apple style, you don’t necessarily need to buy Avenir. You need to adopt their philosophy:

Before introducing San Francisco in 2015, Apple frequently used (specifically a custom variant called Myriad Set ) for its marketing and event slides. 🖋️ Current Primary Font: San Francisco (SF Pro)

is the current standard, Apple has used other typefaces throughout its history: San Francisco (SF Pro)

If you are on a Mac, this font is pre-installed as a system font. If you are on Windows, you can download it from the Apple Developer website.