I have tried installing via the Marketplace and via "Install new software". The result is the same.

Details:
Cannot complete the install because one or more required items could not be found.
Software being installed: Jeeeyul's Themes 2.3.23.I20230324-104319 (net.jeeeyul.eclipse.themes.feature.feature.group 2.3.23.I20230324-104319)
Missing requirement: Jeeeyul's Themes 2.3.23.I20230324-104319 (net.jeeeyul.eclipse.themes.feature.feature.group 2.3.23.I20230324-104319) requires 'org.eclipse.equinox.p2.iu; org.w3c.css.sac 0.0.0' but it could not be found
Do I need to install something else first? Batik :-/?