Sqllite3 doesn't like mysql dump files so a transformation script needs to be run on it. Download https://raw.githubusercontent.com/dumblob/mysql2sqlite/master/mysql2sqlite, make it executable, and run it on the dump file.
".read" returns "memory", which is good.
Clear role_map cache
bundle exec rails c > Rails.cache.delete("RoleMapHash")
SSH into your r6 box, wipeout the database, and load the sqlite dump into your dbconsole.