20 The conjunction δέ (de) is found in 𝔓46 א*,2 A D1 Ψ 1739 1881 𝔐 sy bo, while γάρ (gar) is the conjunction of choice in א1 B D*,c F G 33 lat sa. There are thus good representatives on each side. Scribes generally tended to prefer γάρ in such instances, most likely because it was more forceful and explicit. γάρ is thus seen as a motivated reading. For this reason, δέ is preferred.
21 Grk “brothers,” but the Greek word may be used for “brothers and sisters” or “fellow Christians” as here (cf. ἀδελφός 1, where considerable nonbiblical evidence for the plural ἀδελφοί [adelphoi] meaning “brothers and sisters” is cited).
22 Grk “is not according to man.”

In other versions

For I would have you know, brothers, that the gospel that was preached by me is not man’s gospel.

I want you to know, brothers and sisters, that the gospel I preached is not of human origin.

For I want you to know, brothers and sisters, that the gospel preached by me is not of human origin.

Dear brothers and sisters, I want you to understand that the gospel message I preach is not based on mere human reasoning.

For I make known to you, brothers, the gospel that has been proclaimed by me, that it is not of human origin.

But I certify you, brethren, that the gospel which was preached of me is not after man.

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