Is this still valid in 2019 - Do you earn miles for trips that you flew, but you didn't buy? [duplicate]

In general, yes: you still earn miles for trips you fly regardless of who purchased the ticket. There are many frequent flyer programs around the world, each with fairly complex rules, so you'd have to check the rules of your specific program to know what caveats apply.

One thing that has changed a bit is that more airlines are selling their cheapest tickets in fare classes that don't earn you any frequent flyer miles (sometimes called "basic economy" in the US). These tickets generally come with other limitations (depends on the airline), like prohibiting changes, no advanced seat selection, or no carry-on baggage allowed. If a company is buying basic economy fares for job interview candidates, they're probably either incompetent or hate you, but you'd want to be aware of what fare applies to your ticket to know if you earn miles, and if so, how many.