@seon IMHO this is indeed a problem (I have the same problem) but I also think it's a trade off when to cancel. My guess is, that the conversion is the main time consuming step so maybe "native" ODS format will take less time.
Maybe you can try it. Of course it's not a solution but a step in the right direction.
IMHO the download / backup functionality is still basic because the CryptPad team has so much tasks to do like every open source project.
Anyway, please give feedback so that this thread does not abandon. Thanks.