I see. You're probably right, the categories would be lost. Another reason why it might come in handy to avoid this type of software in the first place, I guess. Not helpful, though. You could choose the lengthy path to enlightenment and export each and every folder/category/you-have-it separately. And learn to avoid proprietary software in the future when they give you no way to choose a different software to work with your data.
Is GrapheneOS a net privacy gain over iOS in my situation?
tango As for your Apple dilemma you could get a Proton account and use Proton drive to store everything. Might be a bit time consuming (like all privacy efforts are) but changing over is simple.
At the moment you can't get more than 500 GB of storage in Proton Drive (as far as I can see), maybe that is not enough for this user. Also, Proton Drive is just a pure storage solution, not a media management software.
I think Piwigo seems very promising, especially if you host it yourself on a TrueNAS system (they have direct support for that) https://piwigo.org/
Then you have a very powerful photo manager. Please note that I have not tried this my self.