I’m not intimately familiar with the Kemper, but I did find a few examples of the Cirrus reverb:
https://youtu.be/x2QKtqOLdTg?t=160
That slow attack, solid sustain, and random modulation … the BlackHole algorithm (or standalone BH pedal) came to mind immediately. Without Pre Delay, maybe starting with the inverse reverb. It’s all about small tweaks of the SIZE & GRAVITY parameters together.
Another option would be the DynaVerb algo, for more control over the attack onset & similar EQ capabilities. It has the ‘ducking’ options lacking in BlackHole.
