Thunder Cannon + Tempest Cleric/Theurge interaction

[8wGremlin]

Ok, ding some messing around and looking at the synergy between the

UA artificers (gunsmiths) 3rd level power

At 3rd level, you learn to channel thunder energy into your Thunder Cannon. As an action, you can make a special attack with your Thunder Cannon that deals an extra 1d6 thunder damage on a hit.This extra damage increases by 1d6 when you reach certain levels in this class: 5th level (2d6), 7th level (3d6), 9th level (4d6), 11th level (5d6), 13th level (6d6), 15th level (7d6), 17th level (8d6), and 19th level (9d6).

and the Tempest Cleric or Tempest Theurge Wizard

Starting at 2nd level, you can use your Channel Divinity to wield the power of the storm with unchecked ferocity.
When you roll lightning or thunder damage, you can use your Channel Divinity to deal maximum damage, instead of rolling.

Can the Channel Divinity maximise the damage of the Thunder Monder, and if so how much would that be?

I did think that a Tempest Cleric/Theurge and a Gunsmith Artificer could be an interesting combo, what are your thoughts?

[MeeposFire]

It would let you maximize the thunder damage from you attack so how much would depend on how many dice your thunder damage is.

For instance if you deal +5d6 thunder damage using your ability if you maximize it you would deal a total of 30 thunder damage with the ability. You would not maximize the weapon damage because it is not thunder damage.