It can use sqlite (single master), or for cluster it can use pg, or mysql, but etcd by default

No, it's not. Read the docs[1] - sqlite is the default.

"Lightweight datastore based on sqlite3 as the default storage backend. etcd3, MySQL, and Postgres are also available."

[1]https://docs.k3s.io/

This thread is about using multi-machine clusters, and sqlite cannot be used for multi-machine clusters in k3s. etcd is the default when starting k3s in cluster mode [1].

[1] https://docs.k3s.io/datastore

No, this thread is about multiple containers across machines. What you describe is multi-master for the server. You can run multple agents across serveral nodes therefore clustering the container workload across multiple container hosting servers. Multi-master is something different.

The very first paragraph of the first comment you replied to is about multi-master HA. The second sentence in that comment is about “every machine is equal”. k3s with sqlite is awesome, but it cannot do that.

apologies, I misread this and gave a terse reply.