Free tier is super limited and super easy to accidentally break out of. I had a single file in S3, but because my logging settings were wrong, I broke the free tier with junk logs.
The t2 micro ec2 instances are fine, but you need to be very careful about their storage and network egress.
Best use I’ve had for AWS that has managed to stay within the free limits has been Lambda. Managed to convert a couple self hosted discord bots to a few Lambda functions, works great. Plugging it into CloudFormation and tying up CI/CD with CodePipeline and the like were overkill but good learning exp.
I don’t think there’s any ECS free tier, but you can fit a private container repository in the free S3 limits as well.