Some articles I’ve bookmarked recently provide some background on nuclear weaponry: the B-52 no longer carries gravity nukes; recap of the capabilities of countries with sea-launched nukes, and losing the nuclear launch codes.
The War Zone – 1/13/20 – The Air Force’s B-52H Bomber Force Has Said Goodbye To Its Nuclear Bombs.
A 2019 update to technical document for strategic bombers says that the B-52H is no longer authorized to carry gravity nuclear bombs. The only weapon it is allowed to carry is the AGM-86B Air Launched Cruise Missile with a W80-1 warhead. The only nuclear loads for the B-2A are the B61-7 and B83-1 gravity bombs, which previously were authorized for the B-52H.