A popular TextBoard running at https://4-ch.net. Perhaps the most popular Western textboard, having survived for... maybe 20 years?
Forums are focused on discussion such as film and TV, Japanese media, music, games... but almost all of these are dead. The most popular boards seem to be /general/, /dqn/, /hobby/, /tech/, and /iaa/.
Good on you if you want to try to breathe live into it. And there's nothing wrong with slow boards, anyway. Just be careful not to get bit by any DqnAnts.