Based on our record, Facebook Design Resources seems to be more popular. It has been mentiond 2 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Spotify isn't doing anything unique here, and it's not really a marketing campaign to explain away their UI. It's more of a showcase for hiring professionals, developers/designers/etc. Facebook has a similar one -> https://design.facebook.com/. Source: almost 3 years ago
Also, read anything published by Design @ Facebook. Source: about 3 years ago
Designer Mill - Collection of Best Free Design Resources
One Knight in Product - Inspiring conversations with passionate product people
Interfacer - Collection of more than 200+ free design resources
Design Details Podcast - A show about the people who design our favorite products.
Freebiesbug - Collection of the best free web design resources.
Immutable Podcast - A short, weekly show about design and development