dig.SPF returns an empty (or near-empty) list for most real domains

dig.SPF returns an empty (or near-empty) list for most real domains: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). I'm trying to use the dig execution module to pull the list of IPs a domain authorizes for sending mail, so I can sync them into firewall rules…