fts-flatcurve will become the default Dovecot Community Edition (CE) FTS driver in v2.4 (merged into Dovecot core in April 2022: https://github.com/dovecot/core/commit/137572e77fdf79b2e8d607021667741ed3f19da1). fts-flatcurve will continue to be maintained in this repository for backwards support with Dovecot CE v2.3.x. However, it is possible that configuration and features may differ between this v2.3 code and core v2.4 code.
Consider depending on
=net-mail/dovecot-2.3*Per @slusarz in the dovecot-fts-flatcurve README.md:
fts-flatcurve will become the default Dovecot Community Edition (CE) FTS driver in v2.4 (merged into Dovecot core in April 2022: https://github.com/dovecot/core/commit/137572e77fdf79b2e8d607021667741ed3f19da1). fts-flatcurve will continue to be maintained in this repository for backwards support with Dovecot CE v2.3.x. However, it is possible that configuration and features may differ between this v2.3 code and core v2.4 code.