Learn Hardcore Korean: oneul achime saeroun dongyeongsangi inteonese eoprodeudwaesseoyo. - A new video was uploaded to the Internet this morning.

오늘 아침 literally means this morning. The particle -에 marks a point in time, so 오늘 아침에 tells us when the action happened (i.e. this morning).

Why is 새로운 used instead of just 새 동영상?

Both 새 동영상 and 새로운 동영상 can mean new video, but there’s a subtle difference in formality and nuance. 새로운 is the full adjective form (새롭다 → 새로운) and feels a bit more natural in standard speech or writing. 새 동영상 is a shortened colloquial version.

Why is 동영상이 marked with the subject particle -이 instead of the object particle -를?

The verb here is 업로드되다, which is a passive verb meaning to be uploaded. In passive constructions, the thing undergoing the action is marked as the subject, so 동영상 takes -이 (subject) rather than -를 (object).

What role does 인터넷에 play? Does -에 imply location or direction?

Here -에 indicates the location or “target space” where the upload ends up. So 인터넷에 업로드됐어요 means it was uploaded onto/to the internet.

How is the verb 업로드됐어요 formed? What are its components?

업로드 is a loanword from English upload.
되다 means to become, and when combined with a noun or loanword it often creates a passive meaning.
The past tense marker -었- plus the polite ending -어요 gives -됐어요 (a contraction of 되어서/되었어요).
All together 업로드 + 되 + 었 + 어요 → 업로드됐어요, meaning (it) got uploaded.

What’s the difference between 업로드됐어요 and 업로드했어요?

업로드됐어요 is passive: it got uploaded (focus on the video as subject).
업로드했어요 is active: I/you/we uploaded (it) (focus on the doer of the action).

How do you pronounce 업로드됐어요, especially the “됐” part?

You’ll hear it as [업-로-드-됐-어-요], where 됐 is pronounced like [되ːŏ] (similar to [됬] in older spelling). The easy way is to link -되- and -었어요 into one syllable: 됐어요 [됐써요].

What level of speech style does the ending -어요 indicate, and how could you change it to be more formal or casual?

The -어요 ending is polite informal (해요체).

To be more formal (존댓말, formal polite), you could say 업로드됐습니다.
To be casual (반말), you could say 업로드됐어.