I was able to work around this by using @angular-builders/custom-webpack and the following configuration in my extra-webpack.config.ts file:

import { Configuration } from 'webpack';

module.exports = async (config: Configuration) => {
    // Make whatever fine-grained changes you need

    config.resolve = { ...config.resolve };

    config.resolve.alias = {
        ...config.resolve.alias,
        // Work around an incorrect require statement in `@progress/telerik-angular-report-viewer` for versions < 12.21.120
        '.\\telerikReportViewer.kendo.min$':
            'node_modules/@progress/telerik-angular-report-viewer/dist/dependencies/telerikReportViewer.kendo.min.js',
    };

    // Return the altered config
    return config;
};

This was finally fixed in @progress/telerik-angular-report-viewer version 12.21.120.