[RPG] Can the spell Booming Blade be affected by the Twinned Spell metamagic

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Booming blade is a Sword Coast Adventurer's Guide cantrip that allows the spellcaster to make a melee weapon attack with their weapon and add additional power to the attack:

You brandish the weapon used in the spell's casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack's normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends

—Booming Blade, Sword Coast Adventurer's Guide, pg. 142

The Twinned Spell metamagic permits a Sorcerer to take any spell that targets only a single creature, and cast it twice, targeting a different creature.

When you cast a spell that targets only one creature and doesn't have a range of self, you can spend a number of sorcery points equal to the spell's level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).

To be eligible, a spell must be incapable of targeting more than one creature at the spell's current level. For example, magic missile and scorching ray aren't eligible, but ray of frost and chromatic orb are.

—Twinned Spell, Player's Handbook, pg. 102

It has been commonly accepted that this is a valid use of this metamagic/cantrip combo, but a recent Errata to the spell has changed its range to "Self (5-foot radius)". Is this spell still eligible to be Twinned?

Best Answer

A range of Self with an area of effect is a further specification.

Booming blade has a range of Self (5 foot radius). Twinned spell says:

When you cast a spell that targets only one creature and doesn't have a range of self

Xirema's answer has alleged that Self (5 foot radius) is not a range of Self with respect to Twinned Spell. This is not the case. The spell still has a range of Self, and an area of effect is further specified. This is clear from the rules for spellcasting, which state:

Spells that create cones or lines of effect that originate from you also have a range of self, indicating that the origin point of the spell's effect must be you (see “Areas of Effect” later in the this chapter).

This rule tells us that spells having a range of self together with a further specification of an area of effect still have a range of self, so are not eligible to be twinned.

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