A trireme can now be upgraded to … whatever it can be upgraded to ?

[Gavroche]

Having played with the classic ruleset for years, I am laboriously adapting to civ2civ3. I even read README.civ2civ3

Trying to learn what a new-style trireme can upgrade to, I check the in-game help and read that it can be

upgraded to Transport or, when possible, to the unit type it upgrades to

What exactly is meant by "when possible, to the unit type it upgrades to" ?

[cazfi]

Having played with the classic ruleset for years, I am laboriously adapting to civ2civ3. I even read README.civ2civ3

Trying to learn what a new-style trireme can upgrade to, I check the in-game help and read that it can be

upgraded to Transport or, when possible, to the unit type it upgrades to

What exactly is meant by "when possible, to the unit type it upgrades to" ?

Oh, Should definitely improve the way help text is generated there (to make it figure out answer to your question, instead of just telling the general rule). In short; Unit upgrade can skip steps. If A upgrades to B, and B upgrades to C, you can upgrade A directly to C (unit type that B upgrades to) if you already know the tech required for C.
I guess that in the current help system you next need to check help for Transport, to see these potential further steps in the upgrade chain.

[cazfi]

Having played with the classic ruleset for years, I am laboriously adapting to civ2civ3.

Oh, btw, civ2civ3 author bard has made a new ruleset civ2civ3_earth. It's sort of more experimental, but also advanced, version of civ2civ3, and available only as a custom modpack. The latest version of that has not yet been available in the modpack installer, as there's a bug in all released freeciv versions that may cause trouble with the ruleset (albeit in a somewhat rare situation). We're going to make that new modpack version available (osdn #48252) along the freeciv-3.0.8 release. And that's supposed to happen... err... just at this very moment, but I'm actually still running some final pre-release tests -> if no issues found in these final tests, we should have the release coming still this night (before I need to switch to bill-paying work - sleep is for youngsters)

[bard]

Oh, btw, civ2civ3 author bard has made a new ruleset civ2civ3_earth. It's sort of more experimental, but also advanced, version of civ2civ3, and available only as a custom modpack. The latest version of that has not yet been available in the modpack installer, as there's a bug in all released freeciv versions that may cause trouble with the ruleset (albeit in a somewhat rare situation). We're going to make that new modpack version available (osdn #48252) along the freeciv-3.0.8 release. And that's supposed to happen... err... just at this very moment, but I'm actually still running some final pre-release tests -> if no issues found in these final tests, we should have the release coming still this night (before I need to switch to bill-paying work - sleep is for youngsters)

Thank you for the publicity , and for allowing this earth variant to be available in the modpack installer.

About the trireme, since it is the only naval unit that can navigate rivers, the capability to upgrade was delayed to prevent that triremes could get trapped when upgraded at cities with river but not sea (that could be problematic for the AI).