Liberapay only allows recurring donations. Liberapay doesn't take a cut, but payment processors they use do. On average about 2.9% for the payments processed by Stripe and 4.9% for the payments processed by PayPal.
Patreon only allows recurring donations. Patreon takes 5%, or 8% or 12% (depending on the plan) of total income creators earn from the platform.
OpenCollective allows recurring donations and one time contributions. OpenCollective takes 10%.
Clarification: It's not OpenCollective that takes 10%, but the project chosen fiscal host that deals will all paperwork regarding taxes, accounting and invoicing.