Need cli command to find the Active LTM device in F5 HA via cli

Try this and tweak the command.

tmsh show /cm device | grep -e "Device" -e "Failover"

-SAM

There are multiple ways to get this,

ltm:Active:In Sync] ~  tmsh show sys failover
Failover active for 50d 19:09:28
ltm:Active:In Sync] ~  tmsh show sys failover | awk '{print $2}'
active
ltm:Active:In Sync] ~  cat /var/prompt/ps1
Active

I agree. tmsh show /sys failover is the best option to verify which device is in active status bu