Hi,
Refusing to review for a closed-access journal is something many subscribers of this list have already done, I suspect.
We made a pledge to help you publicize that stance and encourage others to adopt it:
https://nofreeviewnoreview.org/
It is intended to complement other boycott pledges, without targeting a specific publisher or academic field. We hope you find it useful!
Cheers,
Antonin
openaccess@lists.wikimedia.org