Hello themodelplumber, I'm OP, and the lead (volounteer) developer behind this project. I'm glad you found this project cool, although there are many issues and improvements to do. A given example is the UI that really seems too 90s for 2021 (but it works, and that's the most important thing).

Regarding wkhtmltopdf, yep! It's a nice tool :-) unfortunately we had to apply some hacks for PDF since wkhtmltopdf had a few bugs. We hope to fund some of its development because we need to keep it maintained.

Best!