https://garmoth.com/boss-timer

https://discord.com/invite/bdo

NA Boss Timers discord link also if you prefer getting pings

you can also ask group chat or server chat which boss is next, there is almost always someone available to post the timers and let you know :)

additionally, you can set your in game notifications to alert you when the bosses are coming up by pressing esc - adventure - boss notification

hope this helps!