From https://api.slack.com/custom-integrations/legacy-tokens
Use this tool to download https://github.com/zach-snell/slack-export
wget https://github.com/zach-snell/slack-export/raw/master/slack_export.py
Install dependencies
pip install slacker # https://github.com/os/slacker
pip install pick # https://github.com/wong2/pick
Then run
python3 slack-export.py --token='xoxp-64756569494-[..omitted..]'
After it's done, go into the directory and zip the file, then view in the viewer.
This will take your zip file and host it locally.
pip install slack-export-viewer
Create a zip from the dump, and host it.
cd 20190107-164818-slack_export/
zip -r ../20190107-164818-slack_export.zip *
cd ..
slack-export-viewer -z 20190107-164818-slack_export.zip
Setup nginx to reverse proxy.
sudo certbot --nginx
sudo htpasswd -c /etc/nginx/.htpasswd <username>
# enter password
cat /etc/nginx/.htpasswd # view password