I haven’t seen the ads, but Oracle Cloud is definitely the public cloud provider with the most generous free tier. That’s not to say you should use and trust them, but I can see why many would.
I understand if you have absolutely no money, but even then repeatedly trying to provision a server and getting a error- something like no capacity available - isn't a fun time.
Whatever, I'll pay 7$ a month to not deal with that.
After running every hour for several months I gave up (always out of capacity and it was impossible to change the region on free tier back then). They either had a bug that still showed my account as using the deleted resources or no capacity, both which seem out of place in a “cloud” infrastructure.