Combinations

epslesvou As a variant, you could try the following formula to unpivot your table:

=LET(
    table, DROP(ΑΠΟΣΤΑΣΕΙΣ_ΛΕΣΒΟΣ,, 1),
    row_labels, TAKE(DROP(table, 1),, 1),
    col_labels, DROP(TAKE(table, 1),, 1),
    values, DROP(table, 1, 1),
    VSTACK(
        HSTACK("ΤΟΠΟΣ ΔΙΑΙΤΗΤΗ", "ΓΗΠΕΔΟ", "ΑΠΟΣΤΑΣΗ"),
        HSTACK(TOCOL(IF({1}, row_labels, col_labels)), TOCOL(IF({1}, col_labels, row_labels)), TOCOL(values))
    )
)

Or, as a slightly less verbose option with CHOOSE instead of IF:

=LET(
    table, DROP(ΑΠΟΣΤΑΣΕΙΣ_ΛΕΣΒΟΣ,, 1),
    arr, LAMBDA(n, CHOOSE(n, TAKE(DROP(table, 1),, 1), DROP(TAKE(table, 1),, 1))),
    VSTACK(
        HSTACK("ΤΟΠΟΣ ΔΙΑΙΤΗΤΗ", "ΓΗΠΕΔΟ", "ΑΠΟΣΤΑΣΗ"),
        HSTACK(TOCOL(arr({1})), TOCOL(arr({2})), TOCOL(DROP(table, 1, 1)))
    )
)

See attached...