There's actually an error in the console log when trying to import the html file in 15.x (testing with 15.10.x on my side):
2024-02-15 10:25:25,129 [jodconverter-poolentry-1] ERROR o.j.l.t.LocalConversionTask - Local conversion failed.
java.lang.IllegalArgumentException: Unsupported conversion
at org.jodconverter.core.util.AssertUtils.isTrue(AssertUtils.java:41)
at org.jodconverter.local.task.LocalConversionTask.storeDocument(LocalConversionTask.java:189)
at org.jodconverter.local.task.LocalConversionTask.execute(LocalConversionTask.java:131)
at org.jodconverter.local.office.LocalOfficeManagerPoolEntry.doExecute(LocalOfficeManagerPoolEntry.java:121)
at org.jodconverter.core.office.AbstractOfficeManagerPoolEntry.lambda$execute$0(AbstractOfficeManagerPoolEntry.java:81)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)