https://github.com/r-dbi/RPostgres seems to be the more modern and maintained package at this point. This is what worked for me…
install.packages("RPostgres")
require(RPostgres)
db = dbConnect(
Postgres(),
user="user",
password = 'password',
dbname="dbname",
host="host",
port = port,
sslmode="require"
)
dbListTables(db)