Currently it's impossible to provide custom dictionary files for PostgreSQL full text search.
CREATE TEXT SEARCH DICTIONARY english_hunspell (
TEMPLATE = ispell,
DictFile = en_us,
AffFile = en_us,
Stopwords = english);
ERROR: could not open dictionary file
"/usr/pgsql-12/share/tsearch_data/en_us.dict": No such file or directory
It would be great to have a "tsearch_data files upload" functionality in the managed databases section.
Link to the PostgreSQL doc: