I read that Raspberry Pi now offers an 64 Bit OS for Raspberry 3B. Mine is running already for quite a while and it took me some time to configure my software (main part: Nextcloud) correctly, so I would prefer to keep current package versions and configurations as much as possible. But for now I have only seen the switch with re-flashing the SD card. That would mean I would spent a week (I am not the most clever person on terminal and with linux) to set everything up again.
So: Is there any way to “upgrade” the OS? I.e. replace the OS with a 64 bit system and recompile / install all installed software?