I know of at least one free user who had their account terminated for “inactivity” on a personal basis. I also have read multiple accounts of the Always Free Tier cancelling accounts, even when users are actively using them, for seemingly arbitrary “inactivity” justifications. There are also multiple accounts of them deleting paid user accounts with no warning. My personal anecdotes don't have public stores I can link to, but here's a small collection of people who have had Oracle terminate their accounts for seemingly no reason, or other issues:
The basic details of the problem seem to be:
There are just much safer alternatives, and even ones with reasonable free tiers, like AWS, or with abundant free credits, like DigitalOcean.