6 files declare their use of WebformElementOtherInterface in Webform 6.x

OptionsBase.php in src/Plugin/WebformElement/OptionsBase.php

WebformButtonsOther.php in modules/webform_jqueryui_buttons/src/Plugin/WebformElement/WebformButtonsOther.php

WebformCheckboxesOther.php in src/Plugin/WebformElement/WebformCheckboxesOther.php

WebformRadiosOther.php in src/Plugin/WebformElement/WebformRadiosOther.php

WebformSelectOther.php in src/Plugin/WebformElement/WebformSelectOther.php

WebformSubmissionForm.php in src/WebformSubmissionForm.php