Tempest is just fine indoors.
Call Lightning is the only spell affected, since it requires either an open outdoor area, or an indoor area that is at least 120 feet wide and over 15ish feet tall. (The original requirement of a 100 foot tall ceiling was errata'd out; now you just have to have room overhead for a 10 foot tall cloud.) So you'll occasionally come across large indoor rooms/caves where Call Lightning can still be used.
And you still have Thunderwave and Shatter (upcast and maximized, as needed) for AoE blasting in situations where Call Lightning isn't practical, plus Destructive Wave and Flame Strike, and Spirit Guardians for close-range AoE damage (the latter two are available to all Clerics).
Consider that a Thunderwave or Shatter spell, cast at 3rd level and Maximized, does 32 damage on a failed save. That's 4 points more than the average damage of a 3rd level Fireball from a Light Cleric. A 4th level upcast and maximized Thunderwave/Shatter does 8.5 points more than the average damage of a 4th level upcast Fireball. Granted, Fireball covers a larger area, but the smaller area of Thunderwave/Shatter is handy for careful positioning to avoid friendlies. And they're both doing Thunder damage, which is a less-resisted element than Fire.
Call Lightning does similar maximized damage to Thunderwave/Shatter (30 at 3rd, 40 at 4th), with the big difference being that instead of just doing that damage once, it can do its damage once per round for 10 minutes, all for the cost of one spell slot and your Concentration. (Okay, so no combat is going to last 100 rounds, but it's still very economical...) Only the first two bolts would be able to be Maximized, but then you're still tossing out an average of 16.5/21 damage with the up to 98 subsequent bolts. And since it's Lightning damage, you can push enemies around with those bolts, thanks to your Thunderbolt Strike ability.