I am looking to add support for Arm64 for an open source project, but I don't have resources to setup my own server class hardware infrastructure.
Gabriel,
Although Arm does not directly provide access to hardware resources, there are still a few options available. For example, Arm teamed with Packet to enable the community through the WorksOnArm [1] initiative to gain access to bare-metal platforms. You can submit a request for your open source project via the GitHub page [2]. Once approved, you will be notified for how to access and manage platform(s).
Packet has access to latest partner platforms, enabling developers to optimize and tune software, as well as performing continuous integration and validation.
You can also visit the Arm Developer page for Packet [3], there are a bunch of resources there to explore.
[1]: https://www.worksonarm.com/
[2]: https://github.com/worksonarm/cluster/
[3]: https://developer.arm.com/solutions/infrastructure/developer-resources/development-platforms/packet
Hope this helps!