It does not work in MySQL (8.0.5+) using ICU-REGEXP to perform a search on the word boundary. As far as I understand it should be a-la
$ mysql -e 'SELECT REGEXP_LIKE("aaa abc ccc", ".*\b+abc\b+.*")'
+---------------------------------------------+
| REGEXP_LIKE("aaa abc ccc", ".*\b+abc\b+.*") |
+---------------------------------------------+
| 0 |
+---------------------------------------------+
but this option does not work.