It appears some Lutherans claim apostolic succession. How do they trace their apostolic succession?
At the time of the reformation, many of the bishops of the Church of England, including the Archbishop of Canterbury, Thomas Cramner, were already recognized as consecrated bishops by the Roman church since they had been consecrated prior to the reformation. Apostolic succession in the Anglican communion is traced through these bishops.
The the Churches of Sweden and Finland probably do not claim an unbroken line of laying on of hands, as Gustav I Vasa who converted to Lutheranism, requested the replacement of the Archbishop of Sweden by the Pope, in accordance with the wishes of the Riksdag, which had deposed Gustav Trolle in favor of Johannes Magnus. When the Pope refused, Laurentius Petri was consecrated archbishop of Sweden by the bishop of Vasteras, Petri Magnus. Petri Magnus is said to have been consecrated by the Pope in Rome, which would make for unbroken apostolic succession, however, this is a matter of some dispute.
[The Anglican Chruch's] claim to apostolic succession is rooted in the Church of England's evolution as part of the Western Church. Apostolic succession is viewed not so much as conveyed mechanically through an unbroken chain of the laying-on of hands, but as expressing continuity with the unbroken chain of commitment, beliefs and mission starting with the first apostles; and as hence emphasising the enduring yet evolving nature of the Church. The Anglican—Roman Catholic International Commission report expressed broad agreement in the nature of apostolic succession as the ‘effective sign’ of the apostolicity of the whole people of God, living in fidelity to the teaching and mission of the apostles.