Have Tails Upgrader automatically point to manual upgrade if running from an old version
See #12392 (closed).
“Old” here means “definitely too old to have an IUK”. We are currently publishing IUKs for 2 versions so version older than 12 weeks will never have IUKs.
Note that we might decide to publish more IUKs in the future. So it would be good to have a mechanism in place to remember updating this setting if we decide to ship more IUKs.
This mechanism would also become obsolete if we decide to do #11131 (comment 57704).