If I needed to generate PDFs, I would use ReportLab[1]. The core is open source and there's a great company behind it. The product appears easy and mature. What am I missing?
I have PTSD from 20 years ago trying to convert OpenOffice documents to PDF with ReportLab. It was janky because all elements had to be positioned in absolute coordinates to the virtual page.
Nowadays I'll go straight to https://weasyprint.org to produce PDFs in Python. That's what I used for https://scaleway.com invoices.