doktor5000 wrote:Can you elaborate a bit more on that, why you need to configure them manually in particular ?
Sure, that's my new favorite topic

That computer is a corporate laptop I bring both home and on-site. Our DNS server and firewall are already configured for specific IPs when I'm home. And these IPs are different than the one stable-privacy gives me (and obviously, different than the ones I randomly get from DHCP). A few clients I work with simply don't have DHCP, so I need to provide a static IP when I'm at their place (their place, their rules). When home, DHCP gives me my ISP's DNS server which has two unfortunate flaws: 1. it blocks some websites; 2. it knows nothing about our corporate machines. So I need to use our own DNS server. There's also a very special case when I bring that laptop to my paramour's place but I guess that one is a bit too elaborate.
TL;DR I guess the reason you want to manually configure your IPv6 interface are the same as the reason you want to configure your IPv4 interface.