Rounding up some old news I can confirm that contactless PAYG went live at Bourne End, Cookham, Furze Platt and Marlow on Sunday 22nd May. The news wasn’t particularly broadcast by GWR at the time, and TfL were concentrating on the opening of the Elizabeth line two days later. The fares to these stations are now live in the fare finder on this site.
More recently (12th June) the pink route validators have been activated at Ealing Broadway. These were originally yellow validators so that passengers could start/end a PAYG journey for the Underground and continue via National Rail with a paper ticket. The extension of PAYG to Reading meant that this usage declined, but the impending connection of the Elizabeth line at Paddington with it’s direct link to the Bakerloo line meant that a way needed to be found to show that passengers had avoided zone 1. If changing at Ealing Broadway it’s now advisable to touch the pink reader to ensure that the correct fare is paid.