Trainers will be able to capture a male Frillish this month as part of Niantic’s Research Breakthrough for April 2021.
Here’s how to deal with Gen V monsters.
Research Breakthrough was first introduced in 2018, and it offered Go Trainers a weekly challenge that guaranteed them an encounter with a ‘mon after completing a set of regular tasks.
The title will return to the Unova area in April 2021 to illustrate Water/Ghost-type, Frillish. All of the Field Research tasks that can lead you to the creature are mentioned below.

Every month at the beginning of the month, a new Research Breakthrough is added to the game. Every day, players who log in will be assigned a single Field Research assignment that will reward them with a stamp if they complete it.
Trainers will need to complete these quests over the course of a week to achieve the final target, which will result in an encounter with a male Frillish.
New Field Research tasks are also available from spinning PokeStops, but the game still only allows you to earn one stamp per day.