Got it working.

download-yt-feeds.sh

@@ -0,0 +1,65 @@
+#!/bin/zsh
+# Download YouTube-feeds like they are podcasts.
+# Error codes:
+#   1 = Could not read file or directory.
+#   2 = Configuration option not set.
+
+function die()
+{
+    [[ -n "${2}" ]] && echo "Error: ${2}" >&2
+    exit ${1}
+}
+
+# Return path of configuration directory.
+function get_config_path()
+{
+    local path
+    if [[ -n "${XDG_CONFIG_HOME}" ]]; then
+        path="${XDG_CONFIG_HOME}/download-yt-feeds"
+    else
+        path="${HOME}/.config/download-yt-feeds"
+    fi
+
+    [[ -d "${path}" ]] || mkdir -p "${path}"
+    [[ -r "${path}" ]] || die 1 "${path} is not readable."
+    echo "${path}"
+}
+
+# Return URLs of YouTube-feeds in feedlist.
+# All lines that don't start with "http" are ignored.
+function read_feedlist()
+{
+    local feed_path="$(get_config_path)/feedlist"
+    [[ -r "${feed_path}" ]] || die 1 "${feed_path} is not readable."
+
+    local -a entries
+    while read line; do
+        if [[ "${line}" =~ "^http" ]]; then
+            local -a entry=("${(@s/ /)line}")
+            entries+=(${entry[1]})
+        fi
+    done <"${feed_path}"
+
+    print -r -- ${(qq)entries}
+}
+
+function main()
+{
+    local config_path="$(get_config_path)/config"
+    [[ -r "${config_path}" ]] || die 1 "${config_path} is not readable."
+
+    source "${config_path}"
+    [[ -z "${download_dir}" ]] && die 2 "download_dir not specified."
+    [[ -z "${keep_for_days}" ]] && die 2 "keep_for_days not specified."
+
+    local -a feedlist=("${(@Q)${(z)$(read_feedlist)}}")
+    for feed in ${feedlist}; do
+        youtube-dl \
+            --download-archive "$(get_config_path)/downloaded" \
+            --dateafter "now-${keep_for_days}days" \
+            --output "${download_dir}/%(title)s.%(ext)s" \
+            "${feed}"
+    done
+}
+
+main