On the following page of the AC Valhalla guide you can learn more about the trophies and achievements available in the game. You will find a list of achievements here and learn on which platforms you may collect them.
You will certainly be able to earn achievements on PS4 and Xbox One, as well as on the PC (regardless of the store where you buy the game, it will still require the Uplay platform to work). Copies purchased on PS5 and Xbox Series X platforms should also offer this feature.
After the title is released, a list of all trophies will appear on this page, along with tips to help you unlock them. For more complex achievements, separate pages will be created, entirely dedicated to them.