Yes, REI3 supports full-text search when you use a text attribute and create a text index for it:
https://rei3.de/en/docs/builder#text-indexing
Here is the announcement article for it (look down until you find text indexing):
https://rei3.de/en/news#article-2023-06-19
If you just add a text index, you get a non-language specific ts_vector search. If you also know the language of the text, the full-text search feature can use word-stems as well. For this you would need a second attribute on the same relation (a dictionary attribute), which would store the language of the text.