HLFH [1] filed a deletion request for dovecot-fts-flatcurve [2]: It is currently a -git package. So it is an unoptimized duplicate of https://aur.archlinux.org/packages/dovecot-fts-flatcurve-git, which is more optimised and working as it is working alongside with the dovecot-with-stemmer AUR package. dovecot-fts-flatcurve would never work with dovecot dep as it requires stemmer in the build, which dovecot-with-stemmer currently provides until the dovecot package integrates stemmer in its build. https://gitlab.archlinux.org/archlinux/packaging/packages/dovecot/-/issues/1
[1] https://aur.archlinux.org/account/HLFH/ [2] https://aur.archlinux.org/pkgbase/dovecot-fts-flatcurve/
