“Do you have any URLs or search topics you can recommend?”
No, but I know who to ask.
I don’t have time today to look it up, but yes, there are arguably “missing years” in the Masoric calendar, and a number of opinions in this regard, one of which the Third Ruffian explained.
It is a leading opinion.
Others feel the date is correct, give or take somewhere between 100 and 10,000 years, not millions. (I fall into this camp, in that G-d specifically created Adam at age 34, so he could create a world that is already millions of years old, too.)
Some of this stems from the fact there are “good” records from First Temple forward (with a noted lack of clarity during the Babylonian period) and then wonderful records from Second Temple period from there.
(There is also the matter of “drift” of the calendar itself, in that there were (and are) competing methods of calculating the dates, especially with Karaites. But these are drifts of days within a given year, so not significant in the scale were are talking about.)
As a general consensus, however, it’s trivia and not really important in Judaism.
Someone is right and someone is wrong.
I have enough problems trying to serve G-d and my people, none of which is affected by how old the world is.