Quote from Momijisu >>

 When creating a new line of radiance as an action does it do damage again with the new line?

 Yes, each new line would deal damage as per the first paragraph.

"You can create a new line of radiance as your action on any turn until the spell ends."

The way this spell is written makes it sound like multiple lines of radiance can be cast.  Would the upper limit only be limited by the action economy? If that's the case this would make sunbeam an excellent area denial spell.

Correct, as long as you have actions you can shoot beams. Imagine the sorcerer/fighter combo if an ally casts haste on you.

This spell creates an instantaneous line effect that operates in the same way as a lightning bolt. The effect is not persistent. The ongoing effect of the spell is the ability to fire off another beam each turn, and the radiant light. If it were a persistent sunbeam, the rules for entering and starting your turn in the sunbeam would apply (such as in moonbeam and spirit guardians).

**** you flesh golem

My sorcerer has this spell.  Unfortunately, two of the other players are playing drow characters.  Now it's extremely difficult for me to use it without hindering my allies.  Bruh!  

I didn't realize this spell causes blindness.  I thought the continous 6d8 radiant damage and sunlight was powerful, but it also blinds creatures.  Wow!  Also, undead and oozes have disadvantage on saving throws against this spell, so they are more likely to be blinded.  Noice! 

Final Flash

So a magnifying glass is 100GP in the PHB yet there is no cost listed here, does that mean I can use a focus to cast it at no material cost?

You only need a Material with a specific cost if the spell description mentions one.

This spell only needs a magnifying glass without any cost mentioned. Thus you can use a focus instead.

I just had a 14th Level One Shot where I had my 14th Level Divine Soul Sorcerer use this spell and their Otherworldly Wings to fly around and shoot beams of light out of their eyes (rule of cool).

It was a cool Superman moment.

The Spell which does what everyone thinks Daylight does.

Is Sunbeam a ranged spell attack?

No. Any attack (ranged or melee) requires an attack roll to me made. Sunbeam has an area of effect (5ft wide 60ft long line) and any creature in the line needs to make a saving throw. The spell Magic Missile is an exception to the rule where every dart attack always hits the target and no attack roll is made.

It's crazy that an anti undead spell is only an optional spell for clerics 

I feel like Light Domain clerics should be able to cast it, but since it's too high level for a domain spell, it could just be added to the Cleric spell list.

Quote from EnchantedNinja12345 >>

I didn't realize this spell causes blindness.  I thought the continous 6d8 radiant damage and sunlight was powerful, but it also blinds creatures.  Wow!  Also, undead and oozes have disadvantage on saving throws against this spell, so they are more likely to be blinded.  Noice! 

 I think most oozes are already blind and rely on blindsight, but they'd still be more likely to take full damage. Most undead aren't blind, though, so that would make it more effective on blinding, say, a zombie.

Also, the light produced by that little mote in your hand will damage vampires, so if you're gonna fight one, definitely use this spell.

Tashas Guide made this a Cleric spell.  

Dear DnDBeyond Devs, please update this spell so that I can take it as my Cleric.  

Thank you. 

Does anybody know if the beam stays in existence and is hazardous for any duration? It seems odd that the spell is concentration if all you're doing is shooting another relatively low-damage ray each round while you're concentrating. The description also doesn't say the beam disappears, it just says you make a new one. Any thoughts?

Per RAW, with a Ring of Invisibility, you could cast Sunbeam as a quickened spell.  Then you could use your action to turn invisible.  On your next turn you could create a new line of brilliance, as the spell says, and remain invisible.  Creating a new line of brilliance isn't an attack, it isn't casting a spell since you're already concentrating on the spell, it doesn't require you to take the ring off and you aren't using a bonus action to turn visible again.  These are the 4 conditions upon which you will turn visible again after turning invisible and creating a line of brilliance fits none of them.  Nor does turning invisible with a Ring of Invisibility require concentration because, unlike many other magic items, it isn't allowing you to cast the spell; it simply allows you to have the condition of invisible.  So this is perfectly legal with regard to RAW.