The commit mentioned by Timo has upstream sha1 0e4d354762cefd3e16b4cff8988ff276e45effc4 ("net-next: Fix IP_UNICAST_IF option behavior for connected sockets"), which is claimed to be fixed by 526682b458b1b56d2e0db027df535cb5cdcfde59 ("net: setsockopt: fix IPV6_UNICAST_IF option for connected sockets"). The fix commit was backported to upstream stable v6.0.16.
The commit mentioned by Timo has upstream sha1 0e4d354762cefd3 e16b4cff8988ff2 76e45effc4 ("net-next: Fix IP_UNICAST_IF option behavior for connected sockets"), which is claimed to be fixed by 526682b458b1b56 d2e0db027df535c b5cdcfde59 ("net: setsockopt: fix IPV6_UNICAST_IF option for connected sockets"). The fix commit was backported to upstream stable v6.0.16.