As per Marlene Eilers Koenig, none of the descendants of Carl Eduard, second Duke of Albany, sought the approval required by the Royal Marriages Act. Is there evidence suggesting they did?
Royal Musings: Royal Marriages Act - and who was actually eligible?
Assuming they did not, the grandchildren of Carl Eduard and their descendants are legally illegitimate from the British point of view.
This has also been pointed out in the Peerage News Google group. Apparently the Albany title might be available. But the matter would have to be investigated & the facts established before the title could be used. I suspect the Queen will just avoid it.