Thinktific has its own checkout you can use with its own fees per country and payment gateway used.
https://support.thinkific.com/hc/en-us/articles/360045483433-Thinkific-s-Built-In-Checkout- Netherlands supported https://support.thinkific.com/hc/en-us/articles/1500012376321 Netherlands fees:
- 1.4% + €0.25 - one time payments
- for European Economic Area cards (+1.1% for UK cards)