I'd suggest starting from Volume 25 of the manga. It aligns well with where season 5 ends and takes the story forward smoothly. There might be a few differences in pacing compared to the anime, but it'll give you a seamless continuation.
After season 6 of MHA, a good place to start the manga is around chapter 315. This chapter continues the story arc and keeps you engaged without feeling lost.
One option is to check out official manga subscription services. Sometimes they have the continuation of MHA after season 6. Another possibility is to look for dedicated MHA fan forums or communities where members might share links or information on where to read it.
You can pick up the MHA manga from the chapter that corresponds to the events after season 5. Check online manga platforms or your local comic store for the latest volumes.
Several characters have met their demise in the MHA manga, but it's a bit complex to list them all precisely. Some of the notable ones include [mention specific characters if known].
I think it's hard to say for sure. There are a few characters who could potentially be the traitor, and it's all part of the mystery and suspense of the story.