“Both Clement of Alexandria (革利免, c. AD 150 – 215) and Origen (俄利根, AD 185 – 253) claimed a Pauline association for the book but recognized that Paul himself probably did not put pen to paper for this book, even though they did not know the author’s name. Clement of Alexandria suggests that Paul wrote the book originally in Hebrew and that Luke translated it into Greek, though the Greek of Hebrews bears no resemblance to translation Greek (e.g., that of the Septuagint).” (https://zondervanacademic.com/blog/who-wrote-the-book-of-hebrews)
Eusebius, Hist. Eccl. 6.14.2-3, citing Clement’s Hypotyposes
2. He (Clement) says that the Epistle to the Hebrews is the work of Paul, and that it was written to the Hebrews in the Hebrew language; but that Luke translated it carefully and published it for the Greeks, and hence the same style of expression is found in this epistle and in the Acts.
3. But he says that the words, Paul the Apostle, were probably not prefixed, because, in sending it to the Hebrews, who were prejudiced and suspicious of him, he wisely did not wish to repel them at the very beginning by giving his name.