On a fresh install of 10.4.7 I see the same behaviour.
Some of the borders are still displayed, but it depends on the theme — with Claro a red outer border plus thin grey border between rows, and with Olivero just a red border in between rows. I gather that's due to an update to styles in #3021388 → , and doesn't seem possible to override while using CKEditor5.- 🇨🇦Canada joseph.olstad
@smulvih2, great work on this custom filter that fixes this issue! Amazing! Was ready to call an ambulance after I saw this bug, but now all that is needed is a call to Guiseppe and Bob.