“personal” and “trustless” seem sort of at odds here. you want personal data, so you want personal storage.

what I recommend, if you have the time and energy, is to find another self-hoster you trust and be “backup buddies” with them. set up remote file storage on both your networks and send your backups to the other person’s server.

if you can’t find another self-hoster, then find a friend or family member you trust and mail them your backups on a physical disk.