"Wahrheit" means truth and actually means "tatsächlich" which is the adjective to Tatsache (a fact). So yes "in Wahrheit" is probably best translated with "Actually". Though you could also try it with "In reality" (in Wirklichkeit).
Disclaimer: Also you should be aware that the subreddit ich_iel is a horrible place to learn German. As what they speak would confuse even most Germans.
Basically the meta joke of that subreddit is that they attempt "translate" EVERYTHING into "German"! Where I use "translate" and "German" in air quotes because instead of translating it faithfully they find it hilarious to translate it most directly and impractically so that it is borderline unintelligible to any native German speaker and becomes kind of a guessing game in terms of what meme they translated.
Like "wie ein Geschäftsführer" is German but makes no sense to a person who only speaks German because that's not a meme in Germany, you kinda have to be aware of "like a boss" to figure out what they tried to do there. Or like meme itself which is tranlated to maimai because apparently some older people pronounced it may-may in English so they identified the month of may and translated that to mai.
So a German person speaking German on that subreddit, using regular German words of English origin, especially if they have long entered the German language, is greeted with an ironic "Sprich Deutsch du Hurensohn" (Speak German you son of a bitch), while pure English speakers are usually treated way nicer to avoid confusion though.
So do not take that as a reference for how to speak German as it's basically Germans translating English memes in the most impractical way possible, requiring a solid grasp on English speaking meme culture and German language to understand what they try to do and to find it funny and not to confuse it for an actual translation.