Not who you were responding to but, my company does this in AWS. To be fair, the entire platform is running in EKS so it's not much more difficult than updating the CI build pipelines to build multi-arch containers, adding additional nodepools, and scaling down the amd64 ones. This was tedious but not difficult to do. I keep a small set of amd64 nodes for off the shelf software that doesn't support arm.. I think the only thing left on those now is newrelic agents. Once we move off of them the x86_64 nodes can be killed entirely.

This ended up saving us tens of thousands of dollars per month. The next step is to move the bulk of workloads to spot instances. I'll be preferring arm but if there is only capacity for x86_64, I'll have that option because of the multi-arch containers. This is going to save even more money and force developers to build applications more tolerant of node failure in the process.

If we exclude all cloud providers who sell ARM like Google, Amazon and Oracle. Facebook actively uses ARM at scale and I personally have seen medium size companies (~200-500 employees) using it simply because their backend run fine and it's cheaper.

Vodafone is now into ARM as well: https://www.eenewseurope.com/en/vodafone-fast-tracks-arm-based-chipsets-for-open-ran/

Mobile phone service provider Vodafone has announced it is speeding up the development of chipsets based on the Arm architecture for use in Open Radio Access Networks (Open RAN). At the same time Vodafone told Reuters it continues to work with Intel to create a chipset architecture for Open RAN.