Isaiah 2:2-3 It shall come to pass in the latter days that the mountain of the house of the Lord shall be established as the highest of the mountains, and shall be lifted up above the hills; and all the nations shall flow to it, 3 and many peoples shall come, and say: “Come, let us go up to the mountain of the Lord, to the house of the God of Jacob, that he may teach us his ways and that we may walk in his paths.” For out of Zion shall go forth the law,[a] and the word of the Lord from Jerusalem.
The Jews were intended to be a light to the nations, so the issue of who the law was given to is not necessarily the same as the issue of who the law was intended for. The Mosaic law was given to reveal what sin is, with it we wouldn't even know what sin is (Romans 7:7), and sin is defined as lawlessness (1 John 3:4), so when we are told not to do the things that God has revealed to be sin, then it shouldn't be difficult to figure out what we need to look up to find out what we should avoid doing. Jesus set a perfect example of how to walk in obedience to the law and we are told to follow his example (1 Peter 2:21-22) and to walk in the same way that he walked (1 John 2:3-6). He came with the message to repent from our sins for the kingdom of God is at hand (Matthew 4:17), so repenting from our disobedience to the Mosaic law is a central part of the Gospel message. Our salvation involves being trained by grace to do what God has revealed to be godly, righteous, and good and trained to renounce doing what He has revealed to be ungodly and sinful (Titus 2:11-14), which is essentially what the Mosaic law was given to instruct us how to do (Romans 7:7, Romans 7:12). God has given instructions for how to act according to His holiness, righteousness, and goodness, which are eternal and do not change, and we are followers of the same God, so it is more an issue of who the law was given by than who it was given to.
According to Galatians 5:16-23, everything that is listed as works of the flesh that are against the Spirit are also against the Mosaic law, while everything listed as works of the Spirit are also in accordance with the law, so it doesn't make any sense to interpret Galatians 5:18 as referring to us not being under the Mosaic law, especially when the law was given by God, the Spirit is God, and the Spirit has the role of leading us in obedience to God's law (Ezekiel 36:26-27). Likewise, it doesn't make any sense to interpret Romans 6:14 as referring to the Mosaic law because it is not the Mosaic law which Paul described as sin having dominion over him, but the law of sin, which he contrasted with the Mosaic law (Romans 7:22-23).
All of the 613 laws of the OT and 1,050 laws of the NT can be summed up as instructions for how to love God and how to love our neighbor, so all of the other laws are examples or the explanation for how to correctly obey the greatest two commands. There are more ways to love God and our neighbor than what the law lists, so if we correctly understand the essence of the law or the spiritual principle of love, then our love will go above and beyond what the law requires, but at least do what it requires. We should not follow God's command to love and ignore His commands for how he wants us to love, but rather we should seek to love in the way that He wants us to love according to the example that Jesus gave.
In Romans 7:14, Paul said that the law is spiritual, so while there are no Levites for us to support, we should still follow the same spiritual principles of tithing to support those who work in ministry and to support the poor.