Back in November last year, Spotify was giving out free Google Home Minis to Premium for Family account holders, in order to encourage people to sign up to its plan. The company is renewing its offer this year but is now making it available to both Family and individual subscribers, regardless of whether they're new members or have already been using a paid subscription.
The speaker isn't necessarily the best one to listen to your favorite tunes, but it's a good way to interact with Spotify when your hands are full. I personally use a Home Mini in combination with a cast-enabled speaker, which is an option you could consider if you find your gift a little too limited.
Regarding the offer, it's valid for both Premium Individual and Premium Family master account users in the U.S, including existing ones, while supplies last. The detailed terms and conditions are available on Spotify's site, but they mostly state only paying subscribers can get a free Google Home Mini. Discounted student plans and people who've subscribed through a third party such as their carrier are not eligible for the offer. Lastly, if you already got a free Home Mini last year, you can't get another one this time — sorry.