is the free tier safe?

I know asking this in the protonvpn subreddit is a little biased, but r/VPN doesn't allow the word 'proton' in its posts.

Is the free tier safe to use? 'Free VPN' is essentially a massive red flag in every article I've read. But paying for premium is not something I can do right now (hopefully in the future, I can). I'd like to use it with Next DNS.