I took it in the other direction; I grabbed the stand alone version of the executable from the website, and pointed the
write-data=
at my /home/csmerz/.factorio folder and it seems to be running fine? I lose steam stuff but I'm none too worried about those. I'm just worried that future changes ...

Investigating the different log files, The /home/csmerz/.factorio/ log file (from the original post) shows :

Write data path: /home/csmerz/.factorio [869220/901050MB]

But in the /home/csmerz/snap/steam/common/.factorio/ log (in the latter post), it shows:

Write data path: /home/csmerz/snap ...

Interestingly, The 6 year old files can be found in "~/snap/steam/common/.factorio/saves", so maybe it's getting it's files from the wrong place?

Attaching logfiles from inside the snap folder to this post.

The logfiles from the /.factorio/ folder in the original post seem to show the last time I ...

Certainly possible.

I'm running a relatively stock version of steam & Ubuntu, and everything ran well before. What's weird is that the factorio application "sees" the old saves, but nothing I've done this year. This PC is a new OS build (this year), so those older saves must have come from steam's ...

Hi!
I loaded up Factorio Space Age today, and downloaded the 2.0.20 update using autoupdate on steam, and none of my save files are listed, with the exception of a few pre 1.0 files from 6 years ago. The last time I played was yesterday.

A few more details:
* I'm running the linux version of ...