I've read up on.the "evolutionary phases" that preceeded
SN 1987A.
One thing that struck me was that the final phases for the original
supergiant star [of about 20 solar masses] in the LMC prior to being blown to bits were....

(1) Predominantly carbon fusion [forming Ne, Na, Mg] lasting 1000 years.
(2) Neon fusion [forming O, Mg] lasting several years.
(3) Oxygen fusion [forming Si, S] also lasting several years.
(4) Predominantly silicon fusion [forming Fe] last several days until core collapse.

Number's 2,3,4 indicate that it maybe possible to obtain reliable early-warning of an imminent supernova, offering warning times of at least a
few years down to a few days.

Problem is? What kind of phenomena would be evident in the spectra,
light intensity, neutrino emissions, or external [photospere] temperatures
that can be used to issue a reasonably accurate supernova warning/forecast?

Should we be concerned about an imminent supernova in our galactic
neighborhood?
YES!

The blue supergiant, Rigel [1000 LY distant] and the blue dwarf-giant, Spica [260 LY distant] both have mass values over 10 solar-masses.
Both are also are in the B spectral class, like the pregenitor to SN 1987A.

Both blue giants are clearly fast-burning, metal-rich stars.
I have a strong suspicion that Rigel [whose luminosity is close to that
of SN 1987A during its 1000 year carbon-fusion phase] maybe very close
to a neon & oxygen fusion stage....
Since Rigel is 1000 LY away, it may have ALREADY HAPPENED!
If you're the panicky kind...Well...At least its not Spica, which is 4 times closer.