<html><head></head><body><div>Workaround/ solution:</div><div><br></div><div>Commented out the `inet6 auto` stanza for the interface in /etc/network/interfaces and now it keeps a stable private address as expected. NetworkManager always seemed to yield to ifup/down (or perhaps the reverse) in prior versions of Debian, so I hadn't thought to check there until now.</div></body></html>