The reason there's no vent channel in this Discord server is almost certainly because the moderators are aware that vent channels are extremely likely to turn into radioactive cesspits that attract, retain, and encourage Miserable/Unpleasant People. As this fucking sucks to moderate and has a depressingly high chance to embolden shitty people enough for them to start exporting their fecal matter all over the server, some will simply decline to entertain it at all.
If you realize you can't find a vent channel to use, I gently encourage you to take it as a reminder that where and how you vent matter and public chat channels are generally unproductive (people are unlikely to "complete the circuit" and interact with you in satisfying ways) with heightened risk for further hurt/drama/fallout (because people can see what you said and judge you for it). A private journal or a personal friend are much safer, more private, more productive spaces for processing your emotions. No seriously a physical journal is great, you can write out the ugliest possible feelings onto the page and physically set it on fire later if you want. I feel like people fail to appreciate the cleansing power of immolating their written words these days. Cathartic as can be.
I was in a discord once that had the Only Good Vent Channel. You were only allowed to post strings of the letter A and textless emoji/gifs. So an example post would be:
AAAAAAAAAAAAAAAAAA 🤬😫😖🖕
Purest form of screaming into the void. 10/10.