What safety rule replaced the now-rescinded two-person rule (after Germanwings 9525)? In the aftermath of Germanwings 9525 in 2015 many airlines instituted a two-person rule for the cockpit (aka "two-man rule") - with a flight-attendant replacing whichever pilot left the flight-deck.

In 2017 the industry rescinded that rule. Articles about the repeal of the rules don't mention what alternative processes are being used to prevent another occurrence of sole pilot murder-suicide - or a hypothetical where both pilots have suicidal intent - or when a single pilot is incapacitated while the other pilot is out of the cockpit for medical reasons or other reasons?

The problem being that while the reinforced cockpit door can be opened with an access-code, the occupant of the cockpit can countermand (indefinitely?) the access attempt. Has that policy been changed?

What safety-rule or practices are being instituted to protect against this - or is the pilot murder-suicide scenario being removed from the threat-model entirely? (so if I see one of the pilots banging on the cockpit door while in flight I should resign myself to my fate?)
The French accident investigation board, Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile (BEA), investigated this incident. The report was completed in March 2016. Among the recommendations for EASA was better medical and psychological monitoring by the aero medical examiners. Explicitly not recommended was the already mentioned practice of the two person rule, which leads to the security door being open too many times.

An aero medical examiner recommended that the pilot should have been committed to a mental facility two weeks before the incident. This fact only surfaced during the investigation. So his mental state was detected but because of lax institutional rules, nothing happened. The report can be found at bea.aero.