Where to rent accelerator boards? (fpga as a service)

Here's what I can point you to from the Altera ecosystem:

Cloud/DevCloud Access

Altera's own DevCloud offering lets you access FPGA hardware and development tools in the cloud for testing and validation without local hardware requirements. Altera FPGA Add-on for oneAPI Base Toolkit That's the first place I'd look as it's Altera-native and covers development/validation use cases well.

High-End Partner Accelerator Cards Available in Cloud/Datacenter Contexts

Several high-end Altera-based accelerator boards are purpose-built for the kind of workloads that typically land in cloud/rental infrastructure:

The Terasic Mercury A2700 leverages the Agilex I-Series FPGA with 2700K logic elements, targeting the most compute and bandwidth-demanding applications in the data center, in the cloud, and in embedded devices. Mercury A2700 Accelerator Card It also provides PCIe 5.0 x16 and CXL support, enabling 2× higher bandwidth compared with PCIe 4.0 for higher data throughput, as well as high-speed, low-latency, and efficient performance between CPU and FPGA. Mercury A2700 Accelerator Card

Mobiveil's CXL-Aglx Accelerator platform is a PCIe Gen6 add-in card with the latest Agilex I-Series FPGA, supporting high-performance applications such as Accelerators, Artificial Intelligence, and Machine Learning. CXL Tester

The Silicom BlueFjord FPGA accelerator (FBAP4@AGF series) is a high-performance OEM hardware acceleration platform purpose-built for compute-intensive workloads including cryptographic processing, data compression, and advanced 5G RAN functions such as FEC/LDPC offloading. BlueFjord FBAP4@AGF series FPGA accelerator

Open FPGA Stack (OFS) Ecosystem

If you're looking at platforms with a mature software stack for cloud deployment, OFS is worth evaluating. Open FPGA Stack (OFS) It leverages upstreamed Linux kernel drivers along with the open-source OPAE SDK to accelerate integration into common application frameworks, enabling cross-platform portability and hardware management at runtime Open FPGA Stack (OFS), exactly what you need for elastic, multi-tenant cloud deployments.

I would highly suggest you reach out to your local Altera official distributor to get more information.