I need to stop looking at Mailman2, sigh. I was poking around trying to find subscriber statistics for T281549 and realized that /var/log/mailman/subscribe* has entries going back to August 2020 (log rotate isn't enabled?) and it contains PII, specifically IP addresses. This is way past 90 days as specified in https://meta.wikimedia.org/wiki/Data_retention_guidelines#How_long_do_we_retain_non-public_data?
These log entries are formatted as:
Aug 12 14:03:45 2020 (some number) list name: pending <name> <email> <IP address>