The textual evidence already supplied is rather compelling but it isn't the last word. "Context is king". However, in this case the context agrees that both covenants were ended. It must be plural because Israel, as a nation no longer has any covenant with God anymore since 70AD.
That the Sinai covenant was ended at 70ad is explained in scripture:
[Heb 8:6-13 CSB] 6 But Jesus has now obtained a superior ministry, and to that degree he is the mediator of a better covenant, which has been established on better promises. 7 For if that first covenant had been faultless, there would have been no occasion for a second one. 8 But finding fault with his people, he says: See, the days are coming, says the Lord, when I will make a new covenant with the house of Israel and with the house of Judah -- 9 not like the covenant that I made with their ancestors on the day I took them by the hand to lead them out of the land of Egypt. I showed no concern for them, says the Lord, because they did not continue in my covenant. 10 For this is the covenant that I will make with the house of Israel after those days, says the Lord: I will put my laws into their minds and write them on their hearts. I will be their God, and they will be my people. 11 And each person will not teach his fellow citizen, and each his brother or sister, saying, "Know the Lord," because they will all know me, from the least to the greatest of them. 12 For I will forgive their wrongdoing, and I will never again remember their sins. 13 By saying a new covenant, he has declared that the first is obsolete. And what is obsolete and growing old is about to pass away [IE: in 70ad].
But less commonly accepted is the idea that the new covenant ended then as well. However, when the purpose of the covenant is understood the timing becomes clear.
First of all, the new covenant, like the Sinai covenant was made exclusively with the Israel:
KJV Hebrews 8:10 For this is the covenant that I will make with the house of Israel after those days, says the Lord: I will put my laws into their minds and write them on their hearts. I will be their God, and they will be my people. 11 And each person will not teach his fellow citizen, and each his brother or sister, saying, "Know the Lord," because they will all know me, from the least to the greatest of them. 12 For I will forgive their wrongdoing, and I will never again remember their sins.
What most people seem to miss is that like the first covenant, this is a national covenant, not one made with individuals. It was made with the "houses of Israel and Judah". So what are the implication of that?
Well first of all, the purpose. The purpose of the new covenant was to raise Israel from the dead. For millennia God had railed against Israel through the prophets threatening that the day of their visitation was coming and that they would be destroyed if they didn't repent. Did they repent? Well, no, but God gave them one last chance:
[Zec 13:1 KJV] 1 In that day there shall be a fountain opened to the house of David and to the inhabitants of Jerusalem for sin and for uncleanness.
This was a prediction of John's ministry, calling Israel to repentance before the day of the Lord:
[Mat 3:1-6 KJV] 1 In those days came John the Baptist, preaching in the wilderness of Judaea, 2 And saying, Repent ye: for the kingdom of heaven is at hand. 3 For this is he that was spoken of by the prophet Esaias, saying, The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight. 4 And the same John had his raiment of camel's hair, and a leathern girdle about his loins; and his meat was locusts and wild honey. 5 Then went out to him Jerusalem, and all Judaea, and all the region round about Jordan, 6 And were baptized of him in Jordan, confessing their sins.
But the leadership was blinded and only went through the motions of repentance:
[Mat 3:7-10 KJV] 7 But when he saw many of the Pharisees and Sadducees come to his baptism, he said unto them, O generation of vipers, who hath warned you to flee from the wrath to come? 8 Bring forth therefore fruits meet for repentance: 9 And think not to say within yourselves, We have Abraham to [our] father: for I say unto you, that God is able of these stones to raise up children unto Abraham. 10 And now also the axe is laid unto the root of the trees: therefore every tree which bringeth not forth good fruit is hewn down, and cast into the fire.
This raises the point that "not all Israel is Israel". God actually personally selected 144,000 elect Jews to escape the blinding of Israel (Rom 9-11). Forty days after his death ratified the new covenant these elect received the holy spirit on Pentecost, fulfilling the spiritual meaning of that holiday:
[Col 2:16-17 KJV] 16 Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath [days]: 17 Which are a shadow of things to come; but the body [is] of Christ.
We know that the cities of Sodom and Gomorrah were obliterated by destruction from the Lord. So too Babylon was obliterated, never to be restored. These cities are types of the destruction of Jerusalem and the temple in 70ad,.
The judgment on the Jews was so severe that if God had not spared the elect there would have been no Jews left:
[Isa 1:9 KJV] 9 Except the LORD of hosts had left unto us a very small remnant, we should have been as Sodom, [and] we should have been like unto Gomorrah.
[Rom 9:27 KJV] 27 Esaias also crieth concerning Israel, Though the number of the children of Israel be as the sand of the sea, a remnant shall be saved:
So Israel was dead in trespasses and sins and had to be resurrected and divinely forged into the glorious and holy Israel that God had always intended and had long promised:
[Isa 62:7 KJV] 7 And give him no rest, till he establish, and till he make Jerusalem a praise in the earth.
The outpouring of Pentecost had been predicted as the "last days" of Israel's covenant:
[Act 2:17 KJV] 17 And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams:
Israel was resurrected:
[Eze 37:9-14 KJV] 9 Then said he unto me, Prophesy unto the wind, prophesy, son of man, and say to the wind, Thus saith the Lord GOD; Come from the four winds, O breath, and breathe upon these slain, that they may live. 10 So I prophesied as he commanded me, and the breath came into them, and they lived, and stood up upon their feet, an exceeding great army. 11 Then he said unto me, Son of man, these bones are the whole house of Israel: behold, they say, Our bones are dried, and our hope is lost: we are cut off for our parts. 12 Therefore prophesy and say unto them, Thus saith the Lord GOD; Behold, O my people, I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel. 13 And ye shall know that I [am] the LORD, when I have opened your graves, O my people, and brought you up out of your graves, 14 And shall put my spirit in you, and ye shall live, and I shall place you in your own land: then shall ye know that I the LORD have spoken [it], and performed [it], saith the LORD.
This chosen host were the beneficiaries of the new covenant; they were the "Israel of God". The new covenant provided for them the forgiveness of sins and new heart. They knew Torah without anyone teaching them:
[Act 2:36-41 KJV] 36 Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ. 37 Now when they heard [this], they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men [and] brethren, what shall we do? 38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. 39 For the promise is unto you, and to your children, and to all that are afar off, [even] as many as the Lord our God shall call. 40 And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation. 41 Then they that gladly received his word were baptized: and the same day there were added [unto them] about three thousand souls.
Now, had the new covenant continued then it would still be effective today. However, the Jews have no such army of miracle working army because Israel's unique relationship with God ended in 70ad.
What a fearful, dark and terrible was the day of their visitation:
- the temple was destroyed
- a third or more of the Jews were killed by the Romans
- the city was burned
But the elect fulfilled Israel's destiny and then ended as a distinct covenant entity and was merged with the gentile in the body of Christ, which is based on faith without works.