This stuff again... uh oh.
Acts 2 is the key about the cloven tongue of Pentecost. That MUST be used to define the true cloven tongue per God's Word. If it manifests in any other way, then that's not the true cloven tongue of Pentecost.
How did it manifest concerning language on Pentecost?
Everyone present heard the Apostles speaking not just in the people's own language of birth, but even in the dialects of their languages of birth where they were born. The cloven tongue is the pure speech that all nations and peoples once spoke prior to the tower of Babel event when God confused it into separate languages.
In Acts 2, Apostle Peter quoted from Joel 2, saying, "But this is that which was spoken by the prophet Joel" (Acts 2:16)
The words, "... this is that..." means an example of. It did not mean all those events in Joel 2 were then happening on Pentecost, which is very important to note:
Joel 2:28-32
28 And it shall come to pass afterward, that I will pour out My spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions:
29 And also upon the servants and upon the handmaids in those days will I pour out My spirit.
30 And I will shew wonders in the heavens and in the earth, blood, and fire, and pillars of smoke.
31 The sun shall be turned into darkness, and the moon into blood, before the great and the terrible day of the LORD come.
32 And it shall come to pass, that whosoever shall call on the name of the LORD shall be delivered: for in mount Zion and in Jerusalem shall be deliverance, as the LORD hath said, and in the remnant whom the LORD shall call.
KJV
Those events in bold that Peter quoted did not happen on Pentecost in his days. They are meant for the very end of this world, i.e., the tribulation timing just prior to the "day of the Lord" with our Lord Jesus' second coming.
Here is one of the Scriptures about the very end during the tribulation that the cloven tongue is actually purposed for in the end:
Mark 13:9-13
9 But take heed to yourselves: for they shall deliver you up to councils; and in the synagogues ye shall be beaten: and ye shall be brought before rulers and kings for My sake, for a testimony against them.
10 And the gospel must first be published among all nations.
11 But when they shall lead you, and deliver you up,take no thought beforehand what ye shall speak, neither do ye premeditate: but whatsoever shall be given you in that hour, that speak ye: for it is not ye that speak, but the Holy Ghost.
12 Now the brother shall betray the brother to death, and the father the son; and children shall rise up against their parents, and shall cause them to be put to death.
13 And ye shall be hated of all men for My name's sake: but he that shall endure unto the end, the same shall be saved.
KJV