In the interests of competing against other cloud providers, Oracle provides one of the most competitive sets of always-free resources around. Most of their competitors only provide free trial services or services with limited run times.
Oracle expanded their list of free services earlier this year, notably adding support for up to four cores of Ampere A1 Compute, either in one machine or spread across up to 4 machines. This is a significant improvement over their free 1 OCPU VMs. These servers are particularly useful for projects that require relatively reliable 24/7 uptime, such as Minecraft servers, periodic web scrapers, web servers, and more. I am already using the service for a few of my own personal projects.
There are few strings attached to these instances. The main catch is that there is no guarantee that Oracle will continue to provide these services indefinitely. At any point, they could transition to paid services only, at which point you would have to pay or migrate off the platform. For small hobbyist projects, this should be of limited concern.