Once IN THE STALL many of the systems necessary to understand the situation are compromised.

Solution = avoid STALLING

If we consider the causality chain, that the STALL is caused by a "lack of sufficient lift", which is caused by the range of the actual "airspeed" and/or "AoA", it may become clear that if we could sense, or measure directly "the lift", and thus the "lack of lift", then that would be perhaps an additional parameter, that would add to the reliability of the STALL detection/calculation mechanism.

Good call.
However how do you identify a real stall from a false stall?

However how do you identify a real stall from a false stall?

3. But the entire talk of climbing/descending leads me to envision such scenarios.

The flight crew reported that the weather was fine and clear and there had been no
turbulence during the flight. At about 1239, the first officer left the flight deck for a
scheduled rest break. The second officer then occupied the right control seat.
At 1240:28, the autopilot disengaged. The crew reported that there was an
associated ECAM3 warning message (AUTO FLT AP OFF) and that they also
started receiving master caution chimes. The captain took manual control of the
aircraft using the sidestick. He reported that he attempted to engage autopilot 2 and
then autopilot 1, but neither action was successful.4 The flight data recorder (FDR)
showed that, during this period, the aircraft’s altitude increased to 37,200 ft before
returning to the assigned level.
The crew reported that they cleared the AUTO FLT message from the ECAM. They
then received a NAV IR1 FAULT message on the ECAM.5 The crew were also
receiving aural stall warning indications at this time, and the airspeed and altitude
indications on the captain’s primary flight display (PFD) were also fluctuating.
Given the situation, the captain asked the second officer to call the first officer back
to the flight deck.
At 1242:27, while the second officer was using the cabin interphone to ask a flight
attendant to send the first officer back to the flight deck, the aircraft abruptly
pitched nose-down. The captain reported that he applied back pressure on his
sidestick to arrest the pitch-down movement. He said that initially this action
seemed to have no effect, but then the aircraft responded to his control input and he
commenced recovery to the assigned altitude. The aircraft reached a maximum
pitch angle of about 8.4 degrees nose-down during the event, and a maximum g
loading of -0.80 g6 was recorded. The aircraft descended 650 ft during the event.
The flight crew described the pitch-down movement as very abrupt, but smooth. It
did not have the characteristics of a typical turbulence-related event and the
aircraft’s movement was solely in the pitching plane. They did not detect any
movement in the rolling plane.
During the initial upset event, the second officer activated the seatbelt sign to ON
and made a public address for passengers and crew to return to their seats and
fasten their seatbelts immediately.
The flight crew reported that, after returning the aircraft to 37,000 ft, they
commenced actions to deal with multiple ECAM messages. They completed the
required action to deal with the first message (NAV IR1 FAULT) by switching the
captain’s ATT HDG (attitude heading) switch from the NORM position to CAPT
ON 3 position, and then cleared that message. The next message was PRIM 3
FAULT.7 The crew completed the required action by selecting the PRIM 3 off,
waiting 5 seconds and then selecting it on again.
At 1245:08, shortly after the crew selected PRIM 3 back on, the aircraft
commenced a second uncommanded pitch-down event. The captain reported that he
again applied back pressure on his sidestick to arrest the pitch-down movement. He
said that, consistent with the first event, that action was initially unsuccessful, but
the aircraft then responded normally and he commenced recovery to the assigned
altitude. The aircraft reached a maximum pitch angle of about 3.5 degrees nosedown,
and descended about 400 ft during the second event. The flight crew
described the event as being similar in nature to the first event, though of a lesser
magnitude and intensity.
The captain announced to the cabin for passengers and crew to remain seated with
seatbelts fastened. The second officer made another call on the cabin interphone to
get the first officer back to the flight deck. The first officer returned to the flight
deck at 1248 and took over from the second officer in the right control seat. The
second officer moved to the third occupant seat.
After discussing the situation, the crew decided that they needed to land the aircraft
as soon as possible. They were not confident that further pitch-down events would
not occur. They were also aware that there had been some injuries in the cabin, but
at that stage they were not aware of the extent of the injuries. At 1249, the crew
made a PAN8 emergency broadcast to air traffic control, advising that they had
experienced ‘flight control computer problems’ and that some people had been
injured. They requested a clearance to divert to and track direct to Learmonth, WA.9
Clearance to divert and commence descent was received from air traffic control.
Figure 1 shows the track of the aircraft and time of key events.

Following the second upset event, the crew continued to review the ECAM
messages and other flight deck indications. The IR1 FAULT light and the PRIM 3
FAULT light on the overhead panel were illuminated. There were no other fault
lights illuminated. Messages associated with these faults were again displayed on
the ECAM, along with several other messages. The crew reported that the messages
were constantly scrolling, and they could not effectively interact with the ECAM to
action and/or clear the messages. The crew reported that master caution chimes
associated with the messages were regularly occurring, and they continued to
receive aural stall warnings.
The captain reported that, following the first upset event, he was using the standby
flight instruments and the first officer’s primary flight display (PFD, see Appendix
A) because the speed and altitude indications on his PFD were fluctuating and he
was unsure of the veracity of the other displayed information. After the second
upset event, he had observed that the automatic elevator trim was not functioning
and he had begun trimming the aircraft manually. He later disconnected the
autothrust and flew the aircraft manually for the remainder of the flight.
The flight crew spoke to a flight attendant by interphone to get further information
on the extent of the injuries. The flight crew advised the cabin crew that, due to the
nature of the situation, they did not want them to get out of their seats, but to use the
cabin interphones to gather the information. At 1254, after receiving advice from
the cabin of several serious injuries, the crew declared a MAYDAY10 and advised
air traffic control they had multiple injures on board, including a broken leg and
some cases of severe lacerations.
The crew continued attempts to further evaluate their situation and, at 1256,
contacted the operator’s maintenance watch unit11, located in Sydney, by
SATPHONE to seek assistance. There were several subsequent communications
during the flight between the flight crew and maintenance watch, who advised that
the various faults reported by the crew were confirmed by data link, but that they
were not able to diagnose reasons for the faults. During one of the conversations,
maintenance watch suggested that the crew could consider switching PRIM 3 off,
and this action was carried out. This action did not appear to have any effect on the
scrolling ECAM messages, or the erratic airspeed and altitude information.

The crew reported that master caution chimes associated with the messages were regularly occurring, and they continued to receive aural stall warnings.

By how the aircraft behaves, of course!

It's my sincerest hope that a professional "pilot" would never have to ask that question! I'm presuming those of you asking it are not pilots, because I can't imagine a pilot who could ever not know if he's stalled, PDQ, after the fact. The fact that recent years have shown us that those kind of pilots do exist - even while they earn their Darwin awards, ought to cause us all to have a really good look.... If any pilots reading here have any doubts, have no doubt that you DO need some training.