I applied a patch and installed from ports:
# pkg_info | grep xapian
dovecot-fts-xapian-1.7.13 full text search plugin for Dovecot\
	using Xapian
xapian-core-1.4.24  search engine library

It seems to have no effect.
Jun 03 08:01:39 doveadm(mailbox@somedomain.org): Debug:\
	Mailbox INBOX: UID 1048: Opened mail because: fts indexing
Segmentation fault


On Fri May 31 15:28:41 2024, Stuart Henderson wrote:
> On 2024/05/31 15:44, Maksim Rodin wrote:
> > Hello
> > After upgrading the machine to 7.5 amd64 doveadm command used for
> > indexing mailboxes does not work anymore:
> 
> Does 1.7.13 work any better? Here's a ports diff.
> 
> Index: Makefile
> ===================================================================
> RCS file: /cvs/ports/mail/dovecot-fts-xapian/Makefile,v
> diff -u -p -r1.19 Makefile
> --- Makefile	25 Feb 2024 11:36:11 -0000	1.19
> +++ Makefile	31 May 2024 14:28:15 -0000
> @@ -1,8 +1,9 @@
>  COMMENT=	full text search plugin for Dovecot using Xapian
>  
> -DIST_TUPLE=	github grosjo fts-xapian 1.7.0 .
> -
> -PKGNAME=	dovecot-${DISTNAME}
> +V=		1.7.13
> +DISTNAME=	dovecot-fts-xapian-$V
> +SITES=		https://github.com/grosjo/fts-xapian/releases/download/$V/
> +WRKDIST=	${WRKDIR}/fts-xapian-$V
>  
>  CATEGORIES=	mail
>  
> Index: distinfo
> ===================================================================
> RCS file: /cvs/ports/mail/dovecot-fts-xapian/distinfo,v
> diff -u -p -r1.10 distinfo
> --- distinfo	25 Feb 2024 11:36:11 -0000	1.10
> +++ distinfo	31 May 2024 14:28:15 -0000
> @@ -1,2 +1,2 @@
> -SHA256 (grosjo-fts-xapian-1.7.0.tar.gz) = ygkBoEvgrNRIxGfCa/MWaFMbrzwlkJXjD99dc/NeS/o=
> -SIZE (grosjo-fts-xapian-1.7.0.tar.gz) = 35121
> +SHA256 (dovecot-fts-xapian-1.7.13.tar.gz) = MF60UgNoctNs3MQN0aI5qKBvE7zRh9RkWeMOm5aL6S4=
> +SIZE (dovecot-fts-xapian-1.7.13.tar.gz) = 37569

-- 
Best regards
Maksim Rodin

С уважением,
Родин Максим