For people living in non-imperialist nations, the fall of imperialism will probably make life somewhat easier, especially since it will make the transition to socialism much, much easier.
Many of us do not live in a communist country and do not have the opportunity or desire to move to one. Therefore, we must stay at home to fight to liberate our homeland.
Because of how bad life is going to decline, what can we do to survive financially, mentally, physically, socially, etc? What can we do in order to help liberate ourselves and our nations?
Perhaps we can look to our comrades many decades ago who conducted successful socialist revolutions in the past for inspiration, like in Cuba, China, Tsarist Russia, African nations, Indochina, Korea, etc. They were fighting in conditions much more dire than ours, or possibly even more dire than our future situation.
How does the “developing world” survive? Look at the poor nations and states. Hell, look at rich states that have people in mass poverty. The difference will be that you’ll know what you lost. Education and fomenting unrest. The ruling classes will continue to spread hate and distraction away from themselves, immigrants, LGBT+, ethnic groups… All of these angry reactionaries are potential comrades. They just need to know the truth of who the real enemy is.
I would add that the ruling classes will also hoard assets and make access to services (like healthcare, education and transportation) more exclusive and probably prohibitively expensive.
The economics of poor nations are probably what imperial core collapse will resemble.
Exploitation will increase with workers rights likely being eroded.
Prices are going to increase, both due to less cheap resources and deindustrialization. Perhaps even with some companies moving to poorer countries where such industries might be in demand and also as a means to avoid potential sanctions/trying to get into better trading regions.
Massive quality of life will see people moving out, with the difference to the periphery being that many who migrated there might return to their countries.
Sanctions and might be used against the imperial core.
Interferences and coups will also lilkely begin happening as well, both from outsiders as well as the better off imperial core countries trying to assert themselves over their neighbours.
Wars are a possibility as well.
And so on.