I just thought some of you might have the same problem I had with chromium 
browser moving to snap.  This is the old location of session files:

  ~/.config/chromium/Default/Current\ Session

This is the new location:

  ~/snap/chromium/current/.config/chromium/Default/Current\ Session

But the old files are still in the old location, they just aren't being 
used.  The "current" directory is a symlink to a directory named "920", 
but I assume that directory name can change.

I sometimes use a perl one-liner to see all of the URLs in all of my tabs. 
Right now both of these work and give different answers:

perl -nwle '$h{$_}++ for /http[[:print:]]+/g; END{print for sort keys %h;}' ~/snap/chromium/current/.config/chromium/Default/Current\ Session

perl -nwle '$h{$_}++ for /http[[:print:]]+/g; END{print for sort keys %h;}' ~/.config/chromium/Default/Current\ Session

I think the new snap chromium imported the old session, but it crashed 
when I started it, and then it lost all the old tabs.  I had a lot of tabs 
open, but I don't think it should crash.  I'll try copying the old files 
to see if I can make it work.

Mike