Can you redirect excess damage from a blocked creature with trample to a planeswalker?

Trample (CR 702.19) allows a creature to assign combat damage beyond what is needed to destroy blockers to the defending player. The rules are explicit that excess trample damage goes to the player, not to any planeswalker the player controls.

Planeswalkers can receive combat damage only when a creature attacks them directly (CR 306.7). In that case, the attacking creature is considered to be attacking the planeswalker, not the player. If that creature has trample and is blocked, any excess trample damage would go to the defending player, not to the planeswalker being attacked — because the player is the 'defending player' in that combat (CR 702.19b).

The old 'redirect to planeswalker' rule was removed in 2019 (with the War of the Spark rules update). Players can no longer choose to redirect combat or non-combat damage from themselves to their planeswalkers. Creatures must now be declared as attacking the planeswalker specifically during the declare attackers step.

Example: Your opponent controls a Garruk Wildspeaker. You attack it with a 10/10 trample creature; your opponent blocks with a 2/2. You must assign 2 damage to the blocker. The remaining 8 tramples to the defending player, not to Garruk — even though Garruk was the original attack target.

So in summary: excess trample damage always goes to the defending player (CR 702.19b), never to a planeswalker, regardless of what was being attacked.