We've added the new official Flarum GDPR extension providing support for account anonymization and data export. These are available in your user account's settings at the bottom as Erase Account and Export Data.
Erase Account takes 30 days to happen automatically but a subset of the mods can manually approve the requests earlier. We'll wait a few days to give people time to cancel. This will delete all the account data and reassign the public data including posts to an automatically created deleted user account to replace your account. We can choose to trigger full erasure for an account where all posts are deleted but will not do that in practice. Posts are public and crawled/archived elsewhere so it wouldn't accomplish much and would ruin a bunch of discussions, so we're using the anonymization method as the default.