Is there any specific reason why you are running such an old kernel?
Anyway, to eliminate polkit as being the cause of the issue please try switching to kernel 6.6 or later. You have 3 LTS kernels currently available that will work with the polkit changes.
To install kernel 6.6:
sudo mhwd-kernel -i linux66
or kernel 6.12:
sudo mhwd-kernel -i linux612
or the recently LTS-listed kernel 6.18:
sudo mhwd-kernel -i linux618
After the new kernel is installed, reboot and see if pamac-manager now works.
Note that this issue was covered in the " Known issues and solutions" section of the most recent update announcement:
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What is a Quark?
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