There is a simple plugin. However, it doesn’t work. Can it be made workable with a simple change since it was updated 6 years ago?
# name: Allow iFrame embedding
# about: Changes X-Frame-Options so the site can be embedded
# version: 1
# authors: bex-team, riking,
Rails.application.config.action_dispatch.default_headers.merge!({'X-Frame-Options' => 'ALLOWALL'})