If I attack with Tryndamere and activate Lotus Trap, does Tryndamere trigger when I dealt enough damage because of Lotus Trap?

Yes, Tryndamere's ability will trigger if the damage dealt to the defending unit (doubled by Lotus Trap) results in 5 or more excess damage being assigned.

Reasoning

1. Tryndamere's Ability: Tryndamere's ability triggers "When I conquer after an attack" and checks if "5 or more excess damage" was assigned to enemy units during that combat damage step.
2. Lotus Trap's Effect: Lotus Trap is a replacement effect that doubles all damage dealt to the chosen unit for the turn.
3. Interaction: According to the rules of damage calculation and replacement effects (referenced in RiftJudge FAQ #10010 and the core combat rules), replacement effects like Lotus Trap modify the amount of damage actually dealt. When Tryndamere attacks, the total damage assigned and dealt to the defender is calculated after applying the Lotus Trap multiplier.
4. Meeting the Condition: Since Tryndamere's ability checks for the excess damage assigned, and that value is determined by the total damage dealt in the combat damage step, the doubled damage counts toward the 5+ threshold required to trigger his ability.

Important Considerations (per RiftJudge FAQs):

• Combat Damage Only: Per FAQ #5311 and #7566, only combat damage assigned during the combat damage step counts toward this requirement. Spell damage does not contribute to the "5+ excess damage" calculation.
• Assignment Required: You must ensure that you are actually assigning damage to a unit; if the unit is removed from the board before combat damage occurs (e.g., via a kill spell), Tryndamere will not have a target to assign excess damage to, and the ability will not trigger (FAQ #4400).
• Combat Cleanup: Damage is dealt, triggers are evaluated based on the result, and then the combat cleanup occurs. The doubling effect of Lotus Trap correctly scales the combat damage dealt, which is then used to satisfy the condition for Tryndamere's ability.