While this has been posted before at https://boards.pbe.leagueoflegends.com/en/c/bugs/VeMjqANo-bandit-mastery-still-being-triggered
I have gotten additional information that may help.
It appears that Bandit, the old mastery, still gives gold on attack of any enemy champion. It is functional as it would be normally on "live". However, it appears that it only gives gold when you have **any support item**. In addition, while I do not have the picture for it, it also works with bots as well. Finally, I have only tested this on Summoner's rift intermediate bots, but I am sure it works in normal games as well.
1. Start up the game, runes/champions shouldn't affect the outcome
2. When choosing an item, make sure to pick either Spellthief's edge, relic shield, or ancient coin.
3. Attack an enemy champion
4. Notice the bandit mastery giving gold - It also counts told the gold for the support item quest
Pictures showing that bandit is triggered only with support items:
https://imgur.com/a/t7r0h (Gragas with grasp) [Targon's Brace]
https://imgur.com/a/5nQRJ (Singed with grasp) [No Support Item]
https://imgur.com/a/YHo8V (Singed with grasp) [Nomad's Medallion]
https://imgur.com/a/5qu8E (Singed with grasp) [Frostfang]
https://imgur.com/a/DTb03 (Taliyah with lethal tempo) [Relic Shield]
Things I do not know:
-If past masteries affect whether or not bandit procs
(please dont get mad at me for the taliyah game)