Learn Spanish (Latin America): Ese sí que es un hallazgo fantástico.

The phrase sí que is used for emphatic affirmation. While Ese es un hallazgo fantástico just means "That is a fantastic find," adding sí que brings a strong emotional emphasis or pushes back against doubt or low expectations. It translates perfectly to "That really is..." or "That sure is..."

Could we change the word order and put sí que at the beginning, like Sí que ese es un hallazgo...?

No, sí que needs to go immediately before the conjugated verb it is emphasizing (in this case, es). The subject (Ese) must come before the sí que structure, though the subject can be dropped entirely if the context is already clear (e.g., Sí que es un hallazgo fantástico).

Since Ese is acting as a pronoun here (meaning "That" on its own), shouldn't it have an accent mark (Ése)?

You might see it written as Ése in older texts or from people who learned the older rules. However, the RAE (the official Spanish language academy) updated its spelling rules in 2010. They stated that accent marks are no longer required on demonstrative pronouns like ese, este, and aquel, because context almost always makes it clear whether it's being used as a pronoun or an adjective.

Is only used for physical objects you find, like an antique or a treasure?