Fuzzy_terms_exception when matching against keyword fields


I'm getting a
ElasticsearchException[Elasticsearch exception [type=fuzzy_terms_exception, reason=Term too complex
when running a fuzzy (AUTO) multi match query with a query String that contains long terms against a keyword field. I identified the same problem for other non-keyword fields as well, which I was able to solve by adding a truncate filter to those fields. However, the truncate filter can't be applied to keywords. I saw that one can specify a custom analyzer in the search request, which could do the truncation, but I think this is not what I should do as there are several other fields in my indices with custom analyzers.

I also saw that one can configure the fuzziness per term length, but only to increase the fuzziness at certain lengths. In my case, I actually want to decrease the fuzziness after a certain term length.

Is there some other way to make ES truncate the terms of the search query for keyword fields?
I'm also using a quite old ES version 7.10.2, but AFAIK the truncate filter also can't be applied to keywords in the newest ES version.