Ideally go for kanban but if that is not possible don't exclude support tasks from sprint. Allocate some percentage of sprint for support tasks. What percentage

Ideally go for kanban but if that is not possible don't exclude support tasks from sprint. Allocate some percentage of sprint for support tasks. What percentage would depend on actual rate of support tickets that you are getting week over week set some target for it and get buy in from management that if there is a significant variation in this mix metrics will be affected. Fixating on metrics doesn't work. For managing humans, human touch is required. I am saying this despite creating a tool for managing metrics. My opinion is that metrics should be used as starting point to dig deeper into your process rather than using them as end goal. In this case if you are consistently getting higher than usual support tasks than it may be indicating some other problem like documentation not being clear in which case you need to improve documentation rather than manage the metrics or it could be a new product launch that would invariably lead to more support tickets until it gets stabilized.