I took note of this quote from George Guthrie’s discussion of authorship:
As with other matters of background we are almost entirely dependent on evidence internal to the book. So, what does the work reveal of its maker?George H. Guthrie, Hebrews, The NIV Application Commentary, Kindle edition
In a way, this is the key issue. If you favor internal evidence, you will doubtless favor someone other than Paul as the author. If, on the other hand, you consider the early patriotic accounts, you are much more likely to consider Paul.
This was underlined for me when David Alan Black asked me this: “So if the book of Hebrews claimed Paul as the author in the text you would accept Paul as author?”
The answer to that is yes, absolutely. The internal evidence would never lead me to Paul apart from external statements, I don’t see enough issues in the text to convince me Paul was not the author if the claim was made in the text, assuming that the claim was textually secure.
I publish Dave’s book The Authorship of Hebrews: The Case for Paul, and I credit editing that book for changing my view from “anyone but Paul” to “unknown, but Paul is an option.” One of the key values of Dave’s book is the discussion of the internal evidence.