You are correct that federal law can bar you from firearms even if state law says it’s ok.

But specifically where federal law bars convicted felons from firearms, it looks to state law to define whether the disposition of your case counts as a conviction. That means certain deferrals and dispositions in one state may bar you, the same disposition may not bar you if it happened in another state if the two states differ on whether they consider that disposition to be a conviction.

In this case, Texas does not consider deferred adjudication to be a conviction. So federal law won’t either. That is, of course, assuming this post has used the exact correct words to describe the disposition of the given case. In my experience, people often use words they like to describe their case status, not knowing the legal differences between what happened to them and the words they’ve chosen.

It is probably wise to consult with a criminal defense attorney with expertise in firearms law. It shouldn’t be an expensive consultation. But they can look at your actual case documents to verify that the details of your case are correctly accounted for in the answer.