I agree with @willembargeman that in the linked documentation it looks like it would be possible to implement with the Cisco-AVPair PSK attributes.
I haven't tried this myself, byI think you should implement the enforcement policy like this:

The values in text to be able to copy and paste:
psk-mode=ascii
psk=%{Authorization:[Guest Device Repository]:Device MPSK}
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Best Regards
Jonas Hammarbäck
MVP Guru, ACEX, ACDX #1600, ACCX #1335, ACX-Network Security
Aranya AB
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Original Message:
Sent: Mar 31, 2025 04:07 AM
From: willembargeman
Subject: Clearpass MPSK and Juniper Mist
I didn't have any experience with this. However, I checked the Juniper documentation and looks like the Cisco-AVPair attribute can be used for this.

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Willem Bargeman
Systems Engineer Aruba
ACEX #125
Original Message:
Sent: Mar 31, 2025 03:08 AM
From: hansoele
Subject: Clearpass MPSK and Juniper Mist
Hi Guys,
Does anyone have any experience with settings up MPSK using Juniper Mist access points?
I've come as far as that clearpass authorizes the connection but Juniper doesn't.
Greetings,
Hans