Decide which incremental upgrade paths we want to manually test as part of our release process
Before 1696d48c we would test all incremental upgrade paths. To take an extreme example, when we’ll release Tails 4.20 there will be more than 2 dozens such upgrade paths. I felt this would take too much of our resources to me, so in 1696d48c I changed the doc to only test the “current stable installed from scratch → version being prepared” upgrade path (which uses the v2 upgrader, v2 UDFs, and a v2 IUK). But perhaps that’s not good enough and we need to find a middle ground.
Another question is whether we want to test “Tails << 4.2 → 4.2 or 4.2.1 → version being prepared”, which is a bit different: the first step uses v1 UDFs and IUKs, while the 2nd step switches to v2 UDFs and IUKs.
After the 4.2.1 release, depending on how things go (now that the IUKs and UDFs have been fixed, presumably, and now that all the UDFs are on the test channel), we can discuss what a suitable trade-off could look like.