Blocks "community" and "participants" were removed in Moodle 3.8 (they were present in 3.7).
Themes "bootstrapbase", "clean" and "more" were removed in Moodle 3.7 (they were present in 3.8).
So they should have been deleted during the upgrade to Moodle 3.8. I think it should be safe to proceed. You could take a database backup first as a precaution.
Ensure that the directories blocks/community, blocks/participants, theme/bootstrapbase, theme/clean and theme/more do not exist in the Moodle source code directory. If they do it suggests that the old Moodle source code was not removed during the upgrade which must be done (step 1) for Moodle to function correctly.