Use an Item is an Action - whether ring, staff, potion, etc, as is Attack. If a character cannot take two Actions in a turn, then it could not both Attack with its multi-attack potential and use the ring. Character classes/features that allow Ise an Item as a Bonus Action could, but few of those have multi-attack. So, potentially Attack once and Use ring could happen but not likely for fighting classes. 

nice

roll a d6 and divide by 2. or a d12 and divide by 4

i like it

The ring reads you use an Action to expend a charge, so that doesnt not apply to an "attack" or bonus action "use item". Using this ring uses your full Action.

A d3 is just a d4 where you reroll 4s

Quote from Paladinh >>

Pardon my ignorance, but I could have sworn that a d3 is a non-existent geometric shape? Should that perhaps read "1d4-1"?

Quote from Paladinh >>

Pardon my ignorance, but I could have sworn that a d3 is a non-existent geometric shape? Should that perhaps read "1d4-1"?

 Yeah I have a D3, it’s used a lot for Call of Cthulhu.

if you make a  ranged spell attack with this ring, do you still deal the damage from the spell? 

Quote from FarwinMageBlood >>

Quote from Paladinh >>

Pardon my ignorance, but I could have sworn that a d3 is a non-existent geometric shape? Should that perhaps read "1d4-1"?

 I have seen D3s

 how would that look?

This is not true. Three sides ids possible they are non-rectangular. It would look like a triangle from the side, but the end nearest you and furthest from you would come to a point. From the side, it would look like an oval shape which is pointed on both ends (rounded could work as well).

Is there any ay to put this item on your character sheet and roll a ranged spell attack at +7? It seems like in custom attack entries you can only select the "Stat" i.e. the stat you use to make ranged spell attacks, and the Damage dice. 

Seems impossible to actually add the +7 to your attack roll. 

Quote from place_holderog >>

In brightest day, in blackest night...

 No evil shall escape my sight...

What abilty do you use for the ranged spell attack? Do fighters use strength or dex for example?

According to the free 2024 rules 

*ahem*

D3

The same d notation appears in the expression “1d3,” even though it’s rare to find dice with only three sides. To simulate rolling 1d3, roll 1d6 and divide the number rolled by 2 (round up).

But use whatever crazy ideas that you come up with to simulate a d3. every suggestion in these comments simulate a d3. also if you have some extra cash to blow, buy some dice that have an odd number of sides, they are a lot more fun then using division on a d6.

yeah they are just funky d6s with only 1-3 on all 6 sides.

It's just d6 with two sets of each number

Try 1d6 divided by 2 and rounded up?