Allow sync only to company computers?

Thinking of DSGVO/GDPR I’d like to prohibit installing and syncing the data on users home computers and restrict it to company computers. Is there any way to do something like this?

I think there’s an app for it Restrict login to IP addresses - Apps - App Store - Nextcloud

so you just could limit login for your company network, only.

Our users are often at customer sites (currently mostly at home) so this unfortunately will not work. I don’t want to rely on VPN connections to let it sync.
I think the best way to identify a device would be using certificates of a company CA or something like that.