networkd: How to keep ipv6 RA active but disable autoconf

[contact@xxxxxxxxxx (Anthony Bourguignon)]

Hi,

The configuration with my provider is quite strange. I have to activate
ipv6 RA to obtain a default route. But I don't want to have the address
via autoconf. For that, I use a dhcpv6 pd, with static ip configuration
after that.

Is there a way to activate RA but to disable autoconf ? In my .network
conffile, I've got this :
  IPv6AcceptRA=True
and I've created a file /etc/sysctl.d/local-ipv6.conf :
  net.ipv6.conf.all.use_tempaddr = 0
  net.ipv6.conf.default.use_tempaddr = 0
  net.ipv6.conf.ens3.use_tempaddr = 0
  net.ipv6.conf.all.autoconf = 0
  net.ipv6.conf.default.autoconf = 0
  net.ipv6.conf.ens3.autoconf = 0
  net.ipv6.conf.all.accept_ra_pinfo = 0
  net.ipv6.conf.default.accept_ra_pinfo = 0
  net.ipv6.conf.ens3.accept_ra_pinfo = 0
but I still get an address automatically :
  inet6 xxx::xxx/64 scope global mngtmpaddr noprefixroute dynamic

If I delete it, it reappears after a few seconds.

I wanted to be sure it's not performed by the kernel and so I've put
networkd in debug mode and :
  Jul 10 11:30:33 www systemd-networkd[204]: NDISC: Received Router
Advertisement: flags none preference medium lifetime 15 sec
  Jul 10 11:30:33 www systemd-networkd[204]: NDISC: Invoking callback
for 'r'.
  Jul 10 11:30:33 www systemd-networkd[204]: NDISC: Invalid prefix
length, ignoring prefix for stateless autoconfiguration.
  Jul 10 11:30:33 www systemd-networkd[204]: ens3: Updating address:
xxx:xxx/64 (valid for 4w 2d)

Any tip ?