am not sure if it the bean counters that are of concern
If Elon Must wants the F-35 cancelled and he is as influential as is thought then I wouldn't be confident of the 6th gen fighter development
Killing the F-35 is a semi-popular trope, even used by people who end up buying F-35s. F-35 isn't going anywhere, there is 1000 of them and more orders coming. They can't kill it even if they wanted. They are 20+ years too late.
Future US 6th gen platforms are another thing. Navy looks to be getting one, but beyond that who knows. Same with the B21.. Until orders are places and FOC is seen, very much crystal balling.
UK and Japan (and italy) have a bit of their own issue. They want to keep their industries alive, but F-35 doesn't really do that for them. They also have lots of legacy fighters to be replaced and their own munitions. Their requirements are a bit different. Longer range is of huge interest to each of them either as islands or peninsular. Having something bigger, more sovereign and longer ranged than the F-35 would be genuinely useful for them. So something like a fighter shaped bomber is interesting.
Broadly multirole fighter concept, but with bomber type range. Agility isn't so important anymore for this type of role, but speed is still useful either for dash (which is viable if you have huge internal stores just to outrun) or giving weapons more kinetic energy. Replacing Strike eagles in that kind of concept. There would be others, Singapore, Korea, Saudis, Australia etc.
The B21 is a great plane, but I think it's a bit too focused as a strategic bomber for Australia. We really want something with maritime capabilities with bombing and self escorting functions.
Something that could handle internal AIM-174B would be killer for hunting big slow but valuable air targets at tremendous range. If it could internal that, it could internal significant air to ground weaponry. Internal LRASM would make it a very formidable maritime aircraft. It would also make for a good air patrol aircraft with long range and wide weapon capability. But those are big missiles, not in service with any of those air forces.