Since the Apostle Paul mentioned that God grants repentance to people it would be unnecessary to repeat that point excessively in Scripture. There were far more concerning things for Paul to labor in words & writings with respect to the Jewish people & Gentiles like circumcision, the law of Moses, showing that Jesus is in fact the Christ(Messiah), etc. Especially since the Old Testament deals with the basic concept of repentance already. Jewish people would have been familiar with the concept of repentance, yet not with Christ attached, Christ was very new to 1st century Israel obviously, see: Book of Acts.

Before we get into all of that, let’s address the Scripture that Paul wrote in relation to repentance:

“But avoid foolish and ignorant disputes, knowing that they generate strife. And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will.” 2 Timothy 2:23-26

God speaking through Paul is saying that He alone grants repentance, mankind cannot produce repentance in themselves, just as you also quoted Romans 2:4.

Repentance is mentioned more often in the Book of Acts than the other Pauline corpus.

A few things to consider…

1.) Paul said God manifested His word through preaching, which was committed to him and such preaching involved speaking of repentance to those outside, as you mentioned per (Acts 17:30).

We read: “Paul, a bondservant of God and an apostle of Jesus Christ, according to the faith of God’s elect and the acknowledgment of the truth which accords with godliness, in hope of eternal life which God, who cannot lie, promised before time began, but has in due time manifested His word through preaching, which was committed to me according to the commandment of God our Savior; Titus 1:1-3

All Paul needed to do was preach the Gospel, call sinners to repentance through the fresh revelation he was called to expound upon in 1st first century A.D. Since God alone grants repentance there is no need to constantly hammer such a truth home to those whom he writes to.

2.) Not only that, but for every Epistle Paul wrote; he wrote with an intended purpose. (Example: A letter of rebuke/correction {1&2 Corinthians} or a letter of encouragement {Philemon}.).

Another example is the Epistle to the Galatians. There was such a problem with the Judiazers & their influence upon the Galatian Church that Paul had to correct them of their neglect of the true gospel:

“I marvel that you are turning away so soon from Him who called you in the grace of Christ, to a different gospel, which is not another; but there are some who trouble you and want to pervert the gospel of Christ.” Galatians 1:6-7

According to Galatians 1:1-3 it would appear that Paul was writing to people whom God had already saved & granted repentance to. The issue then wasn’t to call the Churches of Galatia to repentance but to call them to repent of the deliberate straying of the Gospel of Christ .

3.) Just as with the letter to the Ephesians, which was a circular letter intended for more than one church, so too were the 4 Gospels being copied and circulated during Paul’s time. This being the case, Paul & the other Apostles & the early church by extension, would have had the opportunity to preach the words of Jesus in their evangelistic efforts. The Book of Acts reflects such preaching as per the Scripture which records Jesus’s own statements:

“Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying, “The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel.” Mark 1:14-15

“There were present at that season some who told Him about the Galileans whose blood Pilate had mingled with their sacrifices. And Jesus answered and said to them, “Do you suppose that these Galileans were worse sinners than all other Galileans, because they suffered such things? I tell you, no; but unless you repent you will all likewise perish. Or those eighteen on whom the tower in Siloam fell and killed them, do you think that they were worse sinners than all other men who dwelt in Jerusalem? I tell you, no; but unless you repent you will all likewise perish.” Luke 13:1-5

These foundational words from Christ is what propelled the early church to continue that message in evangelism:

“Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call.” Acts 2:38-39

As Paul said also:

“…how I kept back nothing that was helpful, but proclaimed it to you, and taught you publicly and from house to house, testifying to Jews, and also to Greeks, repentance toward God and faith toward our Lord Jesus Christ.” Acts 20:20-21

Paul was more active “testifying to Jews, and also to Greeks… repentance”. Such activity by Paul was more in line with him preaching rather than writing.

4.) Final consideration: The Apostle Paul only had a limited amount of room to write his epistles in terms of the God breathed message The Lord wanted Paul to write. Since “All Scripture is God breathed”(2 Timothy 3:16), God only desired a limited scope of the knowledge of repentance to be revealed in the Pauline Epistles. So if God grants repentance, it’s through the Gospel of Christ since it brings salvation, and salvation, repentance, grace, justification, eternal life, being heirs, receiving mercy, God’s love toward us, all go hand in hand:

“For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes, for the Jew first and also for the Greek. For in it the righteousness of God is revealed from faith to faith; as it is written, “The just shall live by faith.” Romans 1:16-17

Preach the Gospel, and God will use it to bring His elect to faith & repentance.

“For we ourselves were also once foolish, disobedient, deceived, serving various lusts and pleasures, living in malice and envy, hateful and hating one another. But when the kindness and the love of God our Savior toward man appeared, not by works of righteousness which we have done, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit, whom He poured out on us abundantly through Jesus Christ our Savior, that having been justified by His grace we should become heirs according to the hope of eternal life. This is a faithful saying, and these things I want you to affirm constantly, that those who have believed in God should be careful to maintain good works. These things are good and profitable to men.” Titus 3:3-8

Titus 3:3-8 is a prime example of what comes with repentance, not that repentance is mentioned in Titus 3:3-8, but if anyone is to be justified by His grace, they will also be granted repentance or they too will perish (Luke 13:1-5).

CONCLUSION:

The teaching of repentance alongside salvation is a multifaceted reality in Scripture.

“When they heard these things they became silent; and they glorified God, saying, “Then God has also granted to the Gentiles repentance to life.” Acts 11:18.

NOTE: the repentance is to life, obviously a short way to say “eternal life”.