Ultimately you're not going to find a service that can guarantee privacy, but your best bet might be to extract DNA at home (though tricky without a centrifuge etc...) and submit it to a standard sequencing provider novogene, plasmidsaurus etc. Realistically, they'll hold onto the data for a couple of months as part of the order, then delete it to clear up space. A bunch of discordant sets of DNA sequence without metadata isn't exactly useful for nefarious purposes! I wouldn't recommend sequencing at home unless you are very enthusiastic...