A satisfied user of TB on Linux for many years, about 3 months ago I lost many recent messages when transferring from an ancient laptop running Ubuntu to a new laptop running Fedora 42. I installed my entire file system, including the '''.thunderbird''' directory in the home folder, on the new machine from a Duplicity backup of the old machine (BTW, I've now switched to Restic). All my files seemed to be just fine, except that when I opened TB, most messages in local folders that had been received earlier in 2025 were missing. Hoping the problem was a defective backup, I made a new backup of '''.thunderbird''' on the old machine and copied it to the new machine. Nothing changed. Thinking that Duplicity might be failing to backup TB files correctly, I then decided to copy '''.thunderbird''' itself (i.e., the directory and subdirectory structure and all files therein themselves) directly to a USB stick and attempt to restore from that. Unfortunately, the old machine then failed to boot up. Since then I've been making with a big gap in recent email history. With a bit of spare time over the holidays, I've finally managed to boot up the old machine. TB running there shows the messages missing from the new machine. I have copied '''.thunderbird''' to a stick, as I had wanted in September. The problem now is that I cannot simply copy my old TB profile to the new machine, because I'll lose the last 3 months of locally stored email traffic. So, how do I get the lost messages onto my new machine without losing recent messages or creating loads of duplicates?