A [not wildly efficient] script to remove your data from a Slack workspace in lieu of them providing any reasonable means of doing so.

slack_purge.py

# See https://github.com/sgratzl/slack_cleaner2 for instructions on how to install
# the pip library and how to gain an auth token

# When creating the auth token, the app you ccreate needs the following user
# token scopes:
#   - users:read
#   - channels:read
#   - channels:history
#   - chat:write
#   - groups:read
#   - groups:history
#   - im:read
#   - im:history
#   - mpim:read
#   - mpim:history
#   - files:read
#   - files:write

# After getting an auth token, make sure to put it in the `auth_token`
# variable below, as well as putting your Slack username in `your_username`

from slack_cleaner2 import SlackCleaner

auth_token = ""
your_username = ""
s = SlackCleaner("", sleep_for=1)

# Delete all messages and files
for u in s.users:
  if u.name == your_username:
    for f in u.files():
      f.delete()

# Delete all private messages
for c in s.ims:
  for msg in c.msgs():
    if msg.user.name == your_username:
      msg.delete()

# Delete all messages in the general channel
# (duplicate this for other channels as needed)
for msg in s.c.general.msgs(with_replies=True):
  if msg.user.name == your_username:
    msg.delete()

# Alternatively... if you want to delete
# all messages you have posted in every
# channel, uncomment the following block:
#for u in s.users:
#  if u.name == your_username:
#    for m in u.msgs():
#      m.delete()