解决：实现WebMvcConfigurer配置接口的addResourceHandlers方法，为静态资源添加项目路径，解决404问题

// 需添加Configuration注解
package config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class MyInterceptorCfg implements WebMvcConfigurer {

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/community/**").addResourceLocations("classpath:/community/");
    }
}

//引用静态资源
<link rel="stylesheet" th:href="@{/css/global.css}" />

引用：
Spring Boot 配置接口 WebMvcConfigurer