Looking at build.gradle of freshly created such project,
implementation 'io.jmix.core:jmix-core-starter'
implementation 'io.jmix.data:jmix-eclipselink-starter'
implementation 'io.jmix.rest:jmix-rest-starter'
implementation 'io.jmix.security:jmix-security-starter'
implementation 'io.jmix.security:jmix-security-data-starter'
implementation 'io.jmix.localfs:jmix-localfs-starter'
implementation 'io.jmix.authserver:jmix-authserver-starter'
implementation 'org.springframework.boot:spring-boot-starter-web'
seems like if you comment this out from your UI project, it should work
implementation 'io.jmix.flowui:jmix-flowui-starter'
implementation 'io.jmix.flowui:jmix-flowui-data-starter'
implementation 'io.jmix.flowui:jmix-flowui-themes'
Play a bit, if it doesn’t work, copy your rest services code to the new rest only project …
Kind regards,
Mladen