Maybe it's been discussed before, couldn't find it with the search if it was.

What happens when you discard a dual sided card (thanks to Boba Fett (crew) at the moment).

Rules for discarding upgrade cards, per the rules reference:

When an Upgrade card is discarded, it is flipped facedown. The card is out of play for all purposes except when determining the total squad point cost of the ship to which it was equipped. If an Upgrade card is flipped faceup by a game effect, it returns to play equipped to the same ship.

Thanks to the new U-Wing title, we know for certain that dual sided upgrade cards treat both sides as faceup (only faceup cards are considered in play).

Boba Fett forces you to discard a card.

Does that mean Boba Fett can drop your PS by 2 by forcing you to flip Adaptability, or force you to forgo the setup of a 0 K-Turn?

This is not about optimum choices for Boba Fett, or whether you might see it happen in the wild. It is likely that there will be more dual cards in future, and quite likely more cards that force you to discard an upgrade.

Boba forces you to discard an Upgrade card, not flip it, which means it's out of play for all purposes. Ordinarily you would flip it over to show it has been discarded, but with Dual cards, you really need to place it aside somewhere under the pilot card to show it's out of play because it doesn't have a facedown side.

From page 20.

When an Upgrade card is discarded, it is flipped facedown. The card is out of play for all purposes except when determining the total squad point cost of the ship to which it was equipped. If an Upgrade card is flipped faceup by a game effect, it returns to play equipped to the same ship.

The tourney rules specifically state that dual cards are placed under the pilot card when discarded.

Boba forces you to discard an Upgrade card, not flip it, which means it's out of play for all purposes. Ordinarily you would flip it over to show it has been discarded, but with Dual cards, you really need to place it aside somewhere to show it's out of play because it doesn't have a facedown side.

And previously you did just that: you placed discarded cards aside.

But in the new core set they specifically changed the rule so discarding now means flipping the card over.

The tourney rules specifically state that dual cards are placed under the pilot card when discarded.

And that I had not yet read.

Clunky, but that's not unexpected for FFG. They should really add that to the FAQ as you might expect casual players to see that while disregarding the tournament rules.

They could've left well enough alone and not change the rule in the new core set, dual cards must surely have been in development at that time.