Lost entire MySQL Server. Unsure if "master-slave" or "master-master" - How to tell?
For M-M, both need to be masters and both need to be slaves.  Those need

log_slave_updates
log_bin


These should show something, even if not actively replicating at the moment:

SHOW SLAVE STATUS;
SHOW MASTER STATUS;


If you can't run things on the broken machine, then I suggest you do


Clone the good machine's disk to the bad
Change my.cnf to have a different server_id
Turn on the two flags above
CHANGE MASTER ... on both -- to establish being a Slave, and provide the pwd for the replication 'user'.


Now you will have Master-Master.  (There is not a lot of differences between M-S and M-M, so you may as well go for M-M.)