Gelatinous Cube
Creature — Ooze
Engulf — When this creature enters, exile target non-Ooze creature an opponent controls until this creature leaves the battlefield.
Dissolve — 
: Put target creature card with mana value X exiled with this creature into its owner's graveyard.
Olivier Bernard
Rulings
If a token is exiled this way, it will cease to exist and won't return to the battlefield.
(wotc • 2021-07-23)
If the engulfed creature card leaves exile, perhaps because of the Dissolve ability, it won't return to the battlefield after Gelatinous Cube leaves the battlefield.
(wotc • 2021-07-23)
If Gelatinous Cube leaves the battlefield before its Engulf ability resolves, the target non-Ooze creature won't be exiled.
(wotc • 2021-07-23)
Auras attached to the exiled creature will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled creature will cease to exist. When the card returns to the battlefield, it will be a new object with no connection to the card that was exiled.
(wotc • 2021-07-23)
Printings
Rulings
If a token is exiled this way, it will cease to exist and won't return to the battlefield.
(wotc • 2021-07-23)
If the engulfed creature card leaves exile, perhaps because of the Dissolve ability, it won't return to the battlefield after Gelatinous Cube leaves the battlefield.
(wotc • 2021-07-23)
If Gelatinous Cube leaves the battlefield before its Engulf ability resolves, the target non-Ooze creature won't be exiled.
(wotc • 2021-07-23)
Auras attached to the exiled creature will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled creature will cease to exist. When the card returns to the battlefield, it will be a new object with no connection to the card that was exiled.
(wotc • 2021-07-23)