How can I take PayPal Europe Ltd to court if they’re holding $26,000 for 180 days without a clear reason?

PayPal doesn’t hold money of its client and prevent you from gaining access to it without reason. There always is a reason. This money belongs to you, and it is a liability for PayPal.

The question is why is PP holding to your money. The answer is most likely because of something you may have done (with the account, your KYC, etc.) which you would most likely know in which case you have your answer.

Or

There is something not right with the money. Whatever it is, PP may legally be obligated not to tell you this. It would be a court gag order, it could be an ongoing investigation. It could be a money laundering flag, it can be some many thing, but legally, PP is prevented from disclosing this to you.

You can most certainly file a legal court compliant and ask PP to explain.