Monumental ship burial beneath ancient Norwegian mound predates the Viking Age

Indeed - though the article doesn't really state the boats weren't in existence before the Vikings, it's about ship burials which apparently weren't supposed to exist in Scandinavia until the practice was imported from England. A theory I'd never heard before, but I guess that's on me. In any case, the find in the article seems to contradict that theory.

As for boats, the Viking age has been connected with acquiring sail technology, not so much with boats as such (which have existed for a long time, the rock carvings you linked to show depictions of boat designs which have actually been found in archeological digs, and that indicates that older, different carvings are also true and that boats were used for long distance trade and expeditions a millenium or two, at least, before the Vikings).

If the appearance of efficient sail technology really coincided with the beginning of Viking raids is still in the open I believe.

I know it's frustrating but media sort of reflects the most cautious and the most adventurous opinions of archaeology. Because saying vikings started at 793 is just a safe archaeological opinion, while even the romans built coastal forts along the british east coast to defend against "pirates".

Then the media will turn around and print something absolutely outlandish based on a total hypothesis, just because it attracts clicks.

Well yeah, there definitely was the period and cultural phenomenon called the Nordic Bronze Age, which also seems to closely match the dating of those rock carvings. You can read more about it elsewhere, but we're talking about relative largesse, reach and cultural interaction easily matching or exceeding that of the Vikings, originating and spanning a large part of the Indo-European sphere of dominance from Scandinavia to Mycenaean Greece and even beyond. Making and accumulating bronze itself drove the development of trade networks and connections of pretty extreme reach and complexity, unmatched for a long time after the Bronze Age Collapse.

how did they do it without AI though

That is not an issue, because the tree will have been absorbing freshly made atmospheric carbon-14 until it died, at which point it starts to decay into carbon-12. So carbon-14 dating pinpoints the time of death, if you get the methodology right. We apparently now use accelerator mass spectrometers to just outright count all the atoms of c-14 and c-12. But in the 70s c-14 dating was notoriously tricky and full of pitfalls to with calibration and contamination and estimation, and it looks like we've only reduced the last of those possible sources of errors, the need for estimation, and the rest of it is still sketchy.

Wood stored underwater is a thing. Lots of places use bog wood, drowned trees. Down deep, it just goes on being wood.

Tree ring databases are pretty good. I think they cross calibrate to radio carbon maybe.

Most likely they used trees that had grown for at least 100y, as that's how you get the hardest wood (wood from young trees gets all bent in humid weather)