Unfortunately, Slide is abandoned by the author. He replied to an issue on github saying basically that he has no time to maintain it and that and that the code is a mess and needs to he completely rewritten from scratch so he doesn't recommend anyone else bother. Slowly but surely the bugs are mounting. There's so e new-fangked thing that's leaving blue boxes everywhere and videos are breaking again. And I think he also mentioned that the Play Store won't let him push small bug fixes without making another large change that he has no time to work on so it's defacto dead in the water now and will never be updated.
I've been trying Infinity from time to time which others have mentioned as the new OSS client, but it seems less textual than Slide. Sline also has great navigation that is immediately missed elsewhere.
(At least the Android version, dunno about the iOS)
Go to the hamburger menu > settings > manage your subreddits.
Another mobile option is i.reddit.com.