Hi,
I faced this question recently and discussed it with some colleagues. It turned out that we all can see this behavior with the export option missing when opening the flow section on https://make.powerapps.com/ :
However, working instead from https://make.powerautomate.com/ , for the same flow the option is displayed and working:
Don't know whether it's by intent or a bug, or MS retiring the export functionality successively (hope not) or moving it elsewhere. What makes me think this option might be being retired is that the Import Package option (also only available in https://make.powerautomate.com/) is marked as "legacy":
Can you confirm this for your environments?
Best regards,
PS: The above is what I can see in my current Developer tenant.
