Barbara, thanks for the updated info on London museums, sounds like I need to research this topic before every museum visit! For once AI came through where wandering around the Rijksmuseum website did not.
"You cannot bring your own chairs into the museum beyond a certain size. The Rijksmuseum has restrictions on items brought into the galleries. While small bags (up to A4 size) and strollers are generally allowed, larger items like suitcases, large backpacks, and folding chairs would likely need to be stored in the cloakroom or lockers.
The Rijksmuseum may offer folding chairs for loan or rent. They explicitly state they offer the possibility of borrowing or renting wheelchairs, rollators, walking sticks, or foldable museum stools at the information desk.
A "museum stool" is a small, lightweight folding chair designed for museum visitors. These are likely intended for temporary use while viewing exhibits and may be made available to visitors who need seating assistance.
If you require a chair for medical reasons, contact the museum in advance. You may be able to reserve a wheelchair or a foldable chair by emailing [email protected]."