You might be able to ask for a SQL database export that you could try to import into your own Nextcloud instance (with the same version). But that only works if they isolate accounts to a full instance and not just give people access to a single instance.
Self-hosting
Hosting your own services. Preferably at home and on low-power or shared hardware.
Also check out:
I'm not sure if I understand the last bit.
They could use one Nextcloud server for many users or one Nextcloud server per one user. If the latter, then they could give you control of the database. If the former - they cannot give you the access to the database, as there are other accounts there.
Makes sense. Thank you!
If you don't have server access to the old installation, no. You can probably transfer everything, but you have to check for every app how to export and import data via webgui. I know it works for calendar, contacs and probably more but I don't know about the rest. So it'll likely work but it's not exactly straightforward.
Okay, yeah that sounds a little tedious. I'll think a bit more
If it was me I would stop the service then rsync it locally and run the service with he same setup.