The computer decides - who knows what criteria UEFA put into the Algorithm
Here's the basics from Google AI
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36 clubs enter the league phase.
Teams split into four pots of nine based on their five-year UEFA club coefficient rankings.
Pot 1 contains the highest-ranked clubs.
A team is drawn manually by hand from a pot.
Automated software instantly selects eight random opponents (two from each pot) for that club.
The computer also decides which of those eight matches are played at home and which are away.
The software ensures strict rules are met: clubs cannot play teams from their own association, and can face a maximum of two teams from any single other country.