No I can't. As mentioned above, Swiss wouldn't let me checkin even just for the first flight.

And I definitely can't checkin for UA since they only let you checkin if the first flight on the itinerary is UA operated (however I am able to select seats on UA without checking in - and on other airlines you can do the seat selection part of checkin even if passport/visa checks are needed, they tend to print a "this is not a boarding pass" thing).

Took about 2 seconds to sort out at the airport - but this is still embarassingly bad IT on Swiss's part.