I’m struggling to find where I heard about this, but if you post to Twitter (or I guess it’s X now) and tag @Sync, they should get back in touch with you and offer you a bonus 10GB for the positive outreach.
Since I don’t know about where I heard about the offer originally, the next best thing might be my post which Sync responded to as evidence of the bonus. Along with one or two other bonuses which one may have been a referral, I’m at 17GB on the free account which is pretty decent, and certainly not as burdensome as the referral process one has to go through with Dropbox to grow the free tier there.
They’re a great service from the time I’ve spent with it and worth a go.
It’s definitely worth thinking about your use case and whether a second hand mini-pc of some sort is a better option. Along with the Pi itself many people are probably going to need a new case and quite possibly a power adapter too given the new power profile. An older PC where that’s taken care off, and where you probably have a 120GB SSD included, could be the better option for some people.