You can crypt the data before sending to the upgrade platform. Before it was an external script, and since Odoo 16 you can use the `oboo-bin obfuscate` command, before running the upgrade script.
See `./odoo-bin obfuscate --help` to check how to crypt your custom data and uncrypt after upgrade.
It's not perfect (crypt specific columns rather than full DB) but, unfortunatelly, to operate our upgrade service, we need access to the database. Upgrades are complex and requires testing, fine tuning scripts to your specific use cases, etc.
The other alternative is to not use our services, but do it yourself using upgrade scripts from the community: https://github.com/OCA/OpenUpgrade
See `./odoo-bin obfuscate --help` to check how to crypt your custom data and uncrypt after upgrade.
It's not perfect (crypt specific columns rather than full DB) but, unfortunatelly, to operate our upgrade service, we need access to the database. Upgrades are complex and requires testing, fine tuning scripts to your specific use cases, etc.
The other alternative is to not use our services, but do it yourself using upgrade scripts from the community: https://github.com/OCA/OpenUpgrade