I think the only other way beside changing the ticket owner in the UI is maybe directly via the database.
BUT, that's risky (if you not know what you're doing + have a backup done first!) and takes also time since you first need to figure out the SQL query for changing the ticket owner of a specific ticket.
Or maybe easier it's to replace all tickets that e.g. are associated to the user with the id 27 and associate these ticket e.g. to the user with the id 52. Anyway it's nothing done in a few seconds. But the SQL query way is maybe better also for future cleanup/ticket merge.
If you want to do the SQL query way I suggest to clone your installation and play with the clone instead of the live system/database.