David Guzik: Paul’s quotation of Isaiah 45:23 in Philippians 2:10-11 is an overwhelming evidence of the deity of Jesus Christ. Clearly, in Isaiah 45:23 it is the LORD God speaking (I, the LORD, speak, Isaiah 45:19). Now, Paul clearly puts these high words and this high praise towards Jesus: that at the name of Jesus every knee should bow, of those in heaven, and of those on earth, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father. Additionally, the confess [sic] is made that Jesus Christ is Lord - and the word Lord is the same word used in Paul’s ancient Bible for “LORD” in the Old Testament.
https://enduringword.com/bible-commentary/isaiah-45/
Notice that immediately after Isaiah 45:23 we are told that: They will say of Me, Only in the LORD are righteousness and strength (Isaiah 45:24, NASB). Within the same book (Philippians) Paul would speak of the righteousness (1:11; cf. 3:9) and strength (4:13) of the Lord Jesus.