This is basically a clone of T297422, but for the kafka-main100[1-3] nodes. We'd need to upgrade BIOS/NIC/etc.. to allow a clean reimage of the nodes to Buster (already tested in codfw, it worked nicely).
Let me know a time that could work for you, I'd need 10 mins of time ahead to stop daemons etc.. and we cannot have more than one node down at the time (and 10/15 mins need to pass between one node and the other to let them recover).
Hosts to upgrade:
kafka-main1001 kafka-main1002 kafka-main1003