LAMBDA formula not available

jparada , yes, that's normal. New functionality is deployed by channels, first it is received by limited number of users on Beta channel, next entire Beta (as it is now), next Current Preview channel, etc. The latest one is semi-annual channel which is updated with new functionality twice per year.

All of them are under Office 365 subscription, to shift from one to another you may free of charge, yo only have to accept the risk of that Beta is much less stable compare to semi-annual.

You may check your current channel under File->Account->About Excel. How to shift on insiders channel is at Office Insider , it depend on do you have business or consumer subscription.

Estimated date when it will be available for all channels - nobody knows, even Microsoft, it depends on how new functionality is stable on already deployed channels.