Cannot find the ~/Library/Safari/LastSession.plist file

They more than moved it. The LastSession.plist is no longer used in Safari 18.*. Read the posts here that talk about the files you need to restore from Time Machine and their location. I would make backups of the existing mentioned files so they are not overwritten.

If you do not clear your Safari history frequently, then I wrote a sqlite3 solution that when run like this:

./sql_dtu.zsh > ~/Desktop/Safari_hist.csv

will give you a CSV that has the following fields: timestamp, Title, and URL string. Upon opening with Finder Quick Look in nice tabular format, one can right-click on the URL string, and from the Services menu, select Open URL and that will open a new tab in the default browser.

Code:

#!/bin/zsh

: <<'COMMENT'
Generate a CSV document with headers showing current Safari History
database content. You can view the columnar CSV in a scrollable QuickLook window,
or load it into a spreadsheet

Reference: http://2016.padjo.org/tutorials/sqlite-your-browser-history/

Usage in Terminal:
./sql_dtu.zsh > ~/Desktop/hist.csv

VikingOSX, 2020-07-16, Apple Support Communities, No warranties expressed or implied.
COMMENT

sqlite3 -header -csv $HOME/Library/Safari/History.db \
"SELECT DISTINCT
    datetime(visit_time + 978307200, 'unixepoch', 'localtime') AS visit_time,
    coalesce(nullif(title,''), 'Unavailable') as title, url
FROM
    history_visits
INNER JOIN
    history_items ON
        history_items.id = history_visits.history_item;"
exit 0

Tested with Safari 18.1 on macOS Sequoia v15.1 and Sonoma v14.7.

I upgraded Sonoma 14.7 to Sequoia v15.1 and currently have no Macs running Sonoma. However, I just looked in the ~/Library/Safari folder for Safari 18.1 on Ventura 13.7.1. The LastSession.plist is present.