Hi. Unfortunately, there is no officially supported way to remove them. You can follow Customers/users should be able to replace Elastic logo and customize Kibana themes through advanced setting · Issue #75377 · elastic/kibana · GitHub and Easy way to customize Kibana logo and theme · Issue #17879 · elastic/kibana · GitHub to track the progress.
You can find some un-official recommendations posted on Discuss platform, for example,
Custom Logo Kibana 7.10.0 (guide)
Custom Logo Kibana 7.9.2 (guide)
but there are no guarantees these solutions will work in any other Kibana versions.
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