Even Ryanair is like this. I have seen many rucksacks clearly exceeding the (tiny) dimensions for small bag allowed for free with Ryanair but as long as it is not too obvious or a trolley it will be fine. However, trying to bring a carry-on trolley as your bag without purchase of "Priority and 2 cabin bags" add-on, is likely to fail, i.e. you will be asked to pay at boarding.