How can adverse maneuverability due to a fuel tank behind the rear pressure bulkhead be mitigated in Airbus ZeroE hydrogen plane?
Airbus will store hydrogen by chemically binding it to carbon for a looong time. This way, it can be put into the wings, a belly tank and the horizontal tail and its gradual disappearance during the flight will not shift the center of gravity much.
What the PR department just published is just for political correctness. It has not been thoroughly checked for practicability by the engineering department. Nobody seriously expects to use hydrogen for airliners. The problems of storage are obviously putting it at a huge disadvantage, and your correctly identified issue of storing fuel far from the center of gravity is one of those problems.
When an Airbus is delivered today, its tanks are filled with a blend  containing hydrocarbons from a carbon neutral source. Beluga flights delivering parts between the Airbus plants use this fuel. Virgin Airlines tested a renewable fuel already in 2008 and Lufthansa flights departing from Frankfurt also use it.
Of course, most airlines will refill with regular, mineral oil based kerosene after this fuel has been used up because it is cheaper and availability is much better. But technically there is nothing holding back airlines today to use a carbon-neutral fuel.
Generating hydrogen today is mostly done using natural gas which is not quite as carbon intensive as kerosene but everything but carbon-neutral. Also, the energy source for refining and transporting fuel from renewable sources will make them less than 100% carbon neutral. The current sources for renewable fuels (plant oils and waste materials) are less than optimal and hard to scale up, but work on using direct sequestration from atmospheric carbon dioxide is progressing. Today, we waste excess solar power by shorting it to ground. I know better uses for that excess energy …