I would like to check if its feasible to setup a HA K3S as a stretched cluster across 2 zones. Due to a lack of a odd number of zones, I was wondering if this could be done using an external datastore that would have to be sync-ed across the 2 zones. Any recommendations or shared experience is greatly appreciated.

This is a common setup in conjunction with a hosted DB service that handles the cross-zone replication.

Would it work with MSSQL DB (Always On) as the external datastore?

Currently, no https://docs.k3s.io/installation/datastore lists the supported datastore options.

Tks.