Sorcerous Burst
Cantrip - Evocation (Sorcerer)
Casting Time: Action
Range: 18m
You cast sorcerous energy at one creature or object within range. Make a ranged spell attack against the target. On a hit, the target takes 1d8 damage. If you roll an 8 on a d8 for this spell, you can roll another d8 and add it to the damage. The maximum number of these d8s you can add to the spell’s damage equals your spellcasting ability modifier.

You choose the damage type each time you cast this spell: Acid, Cold, Fire, Lightning, Poison, Psychic, or Thunder.

Cantrip Upgrade: The spell’s damage increases by 1d8 when you reach level 5 (2d8), and again at level 11 (3d8).

(Almost) works as written.
When you deal the damage, game checks how many of these rolls are maximum (8). If you rolled "X" number of 8's, another X spells that deals 1d8 damage is automatically casted, one by one. If you roll a 8 on that hit die too, you cast another spell automatically. This happens until you either stop hitting the max or you casted as many as extra spells as your Charisma modifier. Extra spell casts DO NOT benefit from damage riders, nor they do proc things like lightning charges, arcane acuity etc. 

I made it work this way, because there is no (good) way of doing the calculation and applying it in one big hit. In theory this implementation is just the same anyway. It's also fun seeing extra spells go off.

One more thing to add is, due to the way the game treats the crits, you can't check the result of the original dices. They just get lumped together. For example 1d8 crit doesn't become 1d8+1d8, it becomes a 2d8 whose result is totaled before you see the result of individual dies.
For this reason, when you crit, if you roll a 12 or higher, you get an extra explosion. I chose 12 because hitting a sum of 12 or higher in two d8s has a P(E) of ~0.23 which is really close to P(E) of hitting at least one 8 when rolling two d8's. Obviously, while the chance for explosions are similar, this change shifts the distribution of the results a bit higher since it makes you less likely to hit values around 12..15. But there isn't much I can do to change this and it's a crit, so be it. You also get two explosions if you roll 16 on a crit.

Arcane Eruption
Level: 4 Evocation (Sorcerer)
Casting Time: 1 action
Range: 18m

Churning magical energy explodes in a 20-foot-radius sphere centered on a point you choose within range. When you cast the spell, you select the type of damage dealt by the explosion: Acid, Cold, Fire, Lightning, Poison, Psychic, or Thunder. Each creature in the sphere must make a Dexterity saving throw. On a failed save, a creature takes 6d6 damage of the chosen type. On a successful save, a creature takes half as much damage.
Choose one of those d6s. The number rolled on that die determines a condition that’s applied to each creature that failed the save, as shown below. A creature has the condition until the end of your next turn.

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 4.

d6 Additional Effect

• Incapacitated
• Blinded
• Frightened
• Poisoned
• Charmed
• Deafened
  

When you cast the spell, d6 effect is chosen for you by a roll in the backend and applied to everyone who failed the save.
Deafened does not exist in the game, so I changed it with prone

This spell was Always Prepared in UA5. I think it was added to the Sorcerer Spell List in UA7. I feel like it is borderline unpickable for 6d6 damage at Level 4 Spell Slot (I mean Fireball is 8d6 at 3), so I made it Always Prepared as it was in UA5.

Requirements:
1. Script Extender. 
2. Compatibility Framework
3. Shiv's VFX Library
4. Shiv's VFX Vault
If you only want to use the cantrip, you don't need Shiv's libraries, they are only needed for Arcane Eruption VFX. There are no other good explosion VFX that can be cast in 7 different damage types. Even the one I used explosion radius doesn't exactly match the spell but it will have to suffice for now.

Check out my other mod that brings UA7 Sorcerer Abilities here.

Should be bug free, let me know if you encounter any.
Feel free to change the mod to your liking.