BSD

This is probably not the recommended way but it works.

Do everything below in a OpenBSD 6.6 setup. If you run some other version you can do this using OpenBSD VMM

cd /tmp
ftp https://cdn.openbsd.org/pub/OpenBSD/$(uname -r)/{ports.tar.gz,SHA256.sig}
signify -Cp /etc/signify/openbsd-$(uname -r | cut -c 1,3)-base.pub -x SHA256.sig ports.tar.gz

cd /usr
tar xzf /tmp/ports.tar.gz
cd /usr/ports/sysutils/
cp -r salt salt2019.2.7
cd salt2019.2.7

Edit distinfo

SHA256 (salt-2019.2.7.tar.gz) = d648bcfb7f6c3f2e13b5dfd67dec1043fc25cc72ebebec94b00b1dc5b2e1b873
SIZE (salt-2019.2.7.tar.gz) = 14576515

Edit Makefile

# $OpenBSD: Makefile,v 1.156 2020/10/05 19:46:18 jca Exp $

# optional dependencies
# https://github.com/saltstack/salt/blob/develop/doc/conf.py
# libvirt-python
# py-GitPython
# py-croniter
# py-django
# py-libcloud (cloud-requirements.txt)
# py-mako
# py-mongo
# py-mysql
# py-pyinotify
# py-openssl
# py-redis
# rabbitmq

COMMENT =               remote execution and configuration management system

MODPY_EGG_VERSION =     2019.2.7
REVISION =              0
DISTNAME =              salt-${MODPY_EGG_VERSION}

CATEGORIES =            sysutils net devel

HOMEPAGE =              https://community.saltstack.com/

MAINTAINER =            Jasper Lievisse Adriaanse <[email protected]>

# Apache 2.0
PERMIT_PACKAGE =        Yes

MODPY_PI =              Yes
MODPY_VERSION =         ${MODPY_DEFAULT_VERSION_3}
MODPY_SETUPTOOLS =      No

MODULES =               lang/python

BUILD_DEPENDS =         textproc/py-yaml${MODPY_FLAVOR} \
                        www/py-jinja2${MODPY_FLAVOR} \
                        www/py-requests${MODPY_FLAVOR}

# requirements/base.txt
RUN_DEPENDS =           net/py-msgpack${MODPY_FLAVOR}>=0.5.6 \
                        textproc/py-MarkupSafe${MODPY_FLAVOR} \
                        textproc/py-yaml${MODPY_FLAVOR} \
                        www/py-jinja2${MODPY_FLAVOR} \
                        www/py-requests${MODPY_FLAVOR} \
                        www/py-tornado${MODPY_FLAVOR} \
                        sysutils/py-distro

# requirements/zeromq.txt
RUN_DEPENDS +=          net/py-zmq${MODPY_FLAVOR} \
                        security/py-cryptodome${MODPY_FLAVOR}

# salt/output/progress.py
RUN_DEPENDS +=          devel/py-progressbar${MODPY_FLAVOR}

# salt/modules/x509.py
RUN_DEPENDS +=          security/py-M2Crypto${MODPY_FLAVOR}

# salt/{beacons,modules}/ps.py
RUN_DEPENDS +=          sysutils/py-psutil${MODPY_FLAVOR}

# max openfiles, soft: 3072, hard: 4096; DBus system session running...
TEST_IS_INTERACTIVE =   Yes
PORTHOME =              ${WRKDIST}
TEST_DEPENDS =          databases/py-mysqlclient${MODPY_FLAVOR} \
                        devel/git \
                        devel/py-gitpython${MODPY_FLAVOR} \
                        devel/py-pip${MODPY_FLAVOR} \
                        devel/py-six${MODPY_FLAVOR} \
                        devel/py-virtualenv${MODPY_FLAVOR} \
                        devel/subversion \
                        net/py-libcloud${MODPY_FLAVOR} \
                        net/rabbitmq \
                        sysutils/salt-testing \
                        www/py-CherryPy${MODPY_FLAVOR}

pre-configure:
        ${SUBST_CMD} ${WRKSRC}/salt/returners/zabbix_return.py
        sed -i 's,share/man,man,g' ${WRKSRC}/setup.py
        sed -i 's,^#user: root,user: _salt,' ${WRKSRC}/conf/{master,proxy}

post-install:
        ${INSTALL_DATA_DIR} ${PREFIX}/share/examples
        cp -R ${WRKSRC}/conf ${PREFIX}/share/examples/salt

do-test:
        cd ${WRKSRC} && \
                ${MODPY_BIN} tests/runtests.py -v

.include <bsd.port.mk>

Now we bake the package

make plist
make package

If errors

rm /usr/ports/plist/amd64/salt*

in /usr/ports/sysutils/salt2019.2.7/ run:
make clean=dist
make clean

try again