In 2023 I faced and interesting challenge to update / upgrade an online system that was unmaintained for several years. The target system is a Digital Ocean "droplet" - which is a container-based system but proprietary. Digital Ocean does not provide any tools, mechanisms or advice about transferring Droplets externally.
I ran across an interesting article, which I did not try, that uses block-level copying via DD. https://www.secretbatcave.co.uk/software/exporting-digital-ocean-imagesdroplets-to-xenkvmvmware/
The method I did use was to rsync the data to my private host. Following the example of https://gist.github.com/amalmurali47/c58ef024683cccd242625995b45b7b72