That we are at a stage in our existence that we are not only aware of
such a demise so far in the future, but that some people are even
thinking at all about how to save our distant descendants, or whoever
is here then - assuming here is still here in 5 Billion CE.

I agree with ER that the plans outlined in the paper are missing a lot
of other possibilities for the future of our species and Sol system, but
perhaps way before the Sun starts bloating red, we could use these
concepts for other purposes to make the Sol system more habitable,
and perhaps other systems as well.

And it is not ridiculous to assume that some ETI might also be aware
of their sun's future demise and are doing something about it too.
Perhaps we can detect their own self-preservations activities - or
maybe they will show up in person looking for a place to stay. Hopefully
they won't be too insistent.

I also like the idea James Gunn came up with in his 1972 SF novel, The
Listeners. A civilization around a dying star transmits all the information
it has about itself to Earth as a form of cultural preservation, and our
enlightenment in the process. A society that cannot or will not leave
its dying star system might do this as a way to keep part of itself alive
in a safer place. That may be how we first detect ETI. That may also
be what we do to and for others.