Use the global trigger when entity spawns, and use if blocks and not blocks to check if provided world is not client side, also check if event/target entity is sub/type of the entity that you want to replace, and finally add the procedure template for 'do with 70% chance' and replace the 0.7 with whatever percentage chance divided by 100 you want(50%=0.5, 10%=0.1, 83%=0.83, etc) If all of those conditions are true(either using and blocks or nested if blocks) despawn event/target entity and spawn in the entity you want.
That should work, if it does, edit the name of this forum topic to include the word solved.
Use the global trigger when entity spawns, and use if blocks and not blocks to check if provided world is not client side, also check if event/target entity is sub/type of the entity that you want to replace, and finally add the procedure template for 'do with 70% chance' and replace the 0.7 with whatever percentage chance divided by 100 you want(50%=0.5, 10%=0.1, 83%=0.83, etc) If all of those conditions are true(either using and blocks or nested if blocks) despawn event/target entity and spawn in the entity you want.
That should work, if it does, edit the name of this forum topic to include the word solved.