#Both Mind Blank and the Ring of Mind Shielding provide an absolute protection against the Dream spell.#

This spell shapes a creature's dreams. Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you. Creatures that don't sleep, such as elves, can't be contacted by this spell. You, or a willing creature you touch, enters a trance state, acting as a messenger. While in the trance, the messenger is aware of his or her surroundings, but can't take actions or move.

 

If the target is asleep, the messenger appears in the target's dreams and can converse with the target as long as it remains asleep, through the duration of the spell. The messenger can also shape the environment of the dream, creating landscapes, objects, and other images. The messenger can emerge from the trance at any time, ending the effect of the spell early. The target recalls the dream perfectly upon waking. If the target is awake when you cast the spell, the messenger knows it, and can either end the trance (and the spell) or wait for the target to fall asleep, at which point the messenger appears in the target's dreams.

 

You can make the messenger appear monstrous and terrifying to the target. If you do, the messenger can deliver a message of no more than ten words and then the target must make a Wisdom saving throw. On a failed save, echoes of the phantasmal monstrosity spawn a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest. In addition, when the target wakes up, it takes 3d6 psychic damage.

 

[...]

###Is there anything else that provides such a protection?###

Both Mind Blank and the Ring of Mind Shielding provide an absolute protection against the Dream spell.

This spell shapes a creature's dreams. Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you. Creatures that don't sleep, such as elves, can't be contacted by this spell. You, or a willing creature you touch, enters a trance state, acting as a messenger. While in the trance, the messenger is aware of his or her surroundings, but can't take actions or move.

If the target is asleep, the messenger appears in the target's dreams and can converse with the target as long as it remains asleep, through the duration of the spell. The messenger can also shape the environment of the dream, creating landscapes, objects, and other images. The messenger can emerge from the trance at any time, ending the effect of the spell early. The target recalls the dream perfectly upon waking. If the target is awake when you cast the spell, the messenger knows it, and can either end the trance (and the spell) or wait for the target to fall asleep, at which point the messenger appears in the target's dreams.

You can make the messenger appear monstrous and terrifying to the target. If you do, the messenger can deliver a message of no more than ten words and then the target must make a Wisdom saving throw. On a failed save, echoes of the phantasmal monstrosity spawn a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest. In addition, when the target wakes up, it takes 3d6 psychic damage.

[...]

Is there anything else that provides such a protection?

Finally, any spell or effect which allows you to temporarily be on a different plane of existance, like Etheralness, Mordenkainen's Magnificent Mansion, or Demiplane will protect you as they prevent the requirement of the Dream spell that:

The target must be on the same plane of existence as you.

Dream states (emphasis mine):

This spell shapes a creature's dreams. Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you. Creatures that don't sleep, such as elves, can't be contacted by this spell. You, or a willing creature you touch, enters a trance state, acting as a messenger. While in the trance, the messenger is aware of his or her surroundings, but can't take actions or move.

If the target is asleep, the messenger appears in the target's dreams and can converse with the target as long as it remains asleep, through the duration of the spell. The messenger can also shape the environment of the dream, creating landscapes, objects, and other images. The messenger can emerge from the trance at any time, ending the effect of the spell early. The target recalls the dream perfectly upon waking. If the target is awake when you cast the spell, the messenger knows it, and can either end the trance (and the spell) or wait for the target to fall asleep, at which point the messenger appears in the target's dreams.

You can make the messenger appear monstrous and terrifying to the target. If you do, the messenger can deliver a message of no more than ten words and then the target must make a Wisdom saving throw. On a failed save, echoes of the phantasmal monstrosity spawn a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest. In addition, when the target wakes up, it takes 3d6 psychic damage.

Dream states (emphasis mine):

This spell shapes a creature's dreams. Choose a creature known to you as the target of this spell. The target must be on the same plane of existence as you. Creatures that don't sleep, such as elves, can't be contacted by this spell. You, or a willing creature you touch, enters a trance state, acting as a messenger. While in the trance, the messenger is aware of his or her surroundings, but can't take actions or move.

If the target is asleep, the messenger appears in the target's dreams and can converse with the target as long as it remains asleep, through the duration of the spell. The messenger can also shape the environment of the dream, creating landscapes, objects, and other images. The messenger can emerge from the trance at any time, ending the effect of the spell early. The target recalls the dream perfectly upon waking. If the target is awake when you cast the spell, the messenger knows it, and can either end the trance (and the spell) or wait for the target to fall asleep, at which point the messenger appears in the target's dreams.

You can make the messenger appear monstrous and terrifying to the target. If you do, the messenger can deliver a message of no more than ten words and then the target must make a Wisdom saving throw. On a failed save, echoes of the phantasmal monstrosity spawn a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest. In addition, when the target wakes up, it takes 3d6 psychic damage.

In addition, an Antimagic field will protect you absolutely from the Dream spell (emphasis mine):

[...] Spells and other magical effects, except those created by an artifact or a deity, are suppressed in the sphere and can't protrude into it. A slot expended to cast a suppressed spell is consumed. While an effect is suppressed, it doesn't function, but the time it spends suppressed counts against its duration.[...]

Since Dream is a spell it cannot protrude into an Antimagic Field.