Just re: Liberapay's fees, 2.9% is their recorded average when using Stripe and 4.9% the average when using PayPal. YMMV based on e.g. donation size (where a small donation will have a higher % fee due to the processing fees being a combination of flat and %), currency / country, etc.
It's still almost always the lowest-fee option when available, but just wanted to be clear that you can't just jump in and expect to see ~3% regardless of circumstance.