Quite a few negative replies [1], so here's a counterpoint -- Quite a few months back someone on here mentioned using the 24GB/4 core thing for a Minecraft server. While I knew Oracle had a cloud offering, I had never looked at it at all but this enticed me to give it a chance. Not for Minecraft, but lots of time I'm doing things like ETC1 compression of massive textures and I don't want to do it on my MBP. I signed up, got the month free trial (with $300 of credit), and spun up the three "always free" instances (two limited 1 core AMD servers and a 4 core 24GB ARM instance, though I couldn't get the latter until like a week after signing up as there was no availability at the time). All three of these have a public IPv4 which is just super surprising.
These have been perfect since and I have had zero problems. Okay the sales guy in the first month was clearly just bothered by the whole thing (and somehow managed to cancel my account in the process of upgrading it to "paid"), but then it was fixed and everything has been perfect since. On that "personal" account I have had $0 of billing, and they are very clear on billing with up to the moment charting and allocation of every penny billed (not to mention that you can of course set alerts. You would have to really not be paying attention to get surprise billing from this). I've done backups, used volumes, and tried out loads of their services and they have "always free" quotas on loads of stuff. Hilariously I now use one of my AMD instances as the management console to run AWS CLI and kubectl controls for my AWS deployments.
It worked perfectly on me. Since then I've done their "Oracle University" programs and then moved two of my client web applications to Oracle on separate paid accounts, where the pricing is incredibly reasonable (especially the lambda-style functionality which just blows me away). I plan on moving more.
[1] I honestly wonder if some of the negative comments might be people trying to dissuade people from discovering something that seems to be Too Much of A Good Thing. Honestly hesitated posting a positive comment on the chance that if too many people run for freebies it might get the program noticed and clamped down on.