Simply put, I interact with an anvil to rename an iron sword, I click on the text field to start renaming it like you normally would but nothing happens, I tried several other items and no matter what I do it seems I can't rename any item using an anvil anymore. I looked at the wiki and nothing I saw mentioned the anvil needing anything more than before to rename items.
Small update, after reading a bit on similar issues, pressing Tab allows me to edit the text field.
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Thank you for your report!
We're actually already tracking this issue at MC-147513, so we will resolve and link this ticket as a duplicate.
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