The m5n.8xlarge is a general-purpose AWS EC2 instance: 32 vCPU and 128 GiB of memory, 4.00 GiB per vCPU. In the name, "m" is the general-purpose line, "5" is the generation, "n" marks enhanced networking and "8xlarge" is the size within the m5n family. It runs on Intel Xeon Platinum 8259 (Cascade Lake) at 3.1 GHz, and AWS introduced it in October 2019. AWS has since shipped m6i, m7i, m8i and m9g; m6i.8xlarge is the direct replacement at this size. No single Spot node covers 32 vCPU and 128 GiB, so the equivalent is a fleet: 2 × gp.vs1.2xlarge, 32 vCPU and 128 GiB in total, $1.90/hr on AWS in US East (N. Virginia), from $0.082/hr on Rackspace Spot. Spot delivers compute as managed Kubernetes, so a node pool of that size is the native shape of the answer rather than a workaround — provided the workload scales horizontally.
Match qualityScale-out match
m5n.8xlarge gives you 32 vCPU and 128 GiB in a single machine. The largest comparable Spot node, gp.vs1.2xlarge, is 16 vCPU and 64 GiB, so the equivalent here is 2 nodes rather than one.
Spot runs as managed Kubernetes, so a 2-node pool is the normal way to run things rather than a workaround. If your workload already sits behind a load balancer, a queue or a scheduler, it spreads across them without changes. If it needs all 32 cores and 128 GiB in one process, it does not.