Hey Simon, J,
after some more searching I’ve finally found a custom solution for you. Please download this archive, unzip it, and upload the contained files into the theme folder (/wp-content/themes/Ikebana/), replacing the existing files. After you refresh the website, the portfolio page template should display native WordPress posts instead of portfolio projects.
Please let me know if it works as intended!
Sincerely,
Andrii / Satori Studio