The Europa League always started from a round of 32 in KO rounds, but only in the last year (since Conference League was started) did they change the format.
This is from Wiki on last seasons EL:
In the knockout phase, teams played against each other over two legs on a home-and-away basis, except for the one-match final. The mechanism of the draws for each round was as follows:
In the draw for the knockout round play-offs, the eight group runners-up were seeded, and the eight Champions League group third-placed teams were unseeded. The seeded teams were drawn against the unseeded teams, with the seeded teams hosting the second leg. Teams from the same association could not be drawn against each other.
In the draw for the round of 16, the eight group winners were seeded, and the eight winners of the knockout round play-offs were unseeded. The seeded teams were drawn against the unseeded teams, with the seeded teams hosting the second leg. Teams from the same association could not be drawn against each other.
In the draws for the quarter-finals and semi-finals, there were no seedings, and teams from the same association could be drawn against each other. As the draws for the quarter-finals and semi-finals were held together before the quarter-finals were played, the identity of the quarter-final winners was not known at the time of the semi-final draw. A draw was also held to determine which semi-final winner was designated as the "home" team for the final (for administrative purposes as it was played at a neutral venue).