fangman said..
In Buddhist philosophy, the First Noble Truth states that "life is suffering" (Dukkha). This concept encompasses the idea that suffering is an inherent part of existence, arising from attachment, desire, and the impermanence of life. It follows that when you are dead you are no longer suffering and therefore at peace.
If it were true that death brings peace we might as well end it now.

There's a Buddhist joke that goes, "Why do we say Rest in Peace to the deceased. Wouldn't it be better to Rest in Peace while we're alive?"
According to the earliest compete text we have on what the Buddha taught which is in the Pali Canon, when you die you could be reborn into one of a number of different realms, some are hellish, some are heavenly, others are neutral. Could be material or immaterial. None are permanent. The only way to stop this process of birth/death (samsara) is to end craving (Nibbana/Nirvana). I'm not saying this because I know it, but that's what is taught in the ancient Buddhist texts. I lived in Buddhist monasteries for a while and learnt this there.
You mentioned the 1st noble truth which is correct. The 3rd noble truth states;
"Now this, bhikkhus, is the noble truth of the cessation of suffering: it is the remainderless fading away and cessation of that same craving, the giving up and relinquishing of it, freedom from it, non-reliance on it."
Basically what it is saying is that the end of suffering is realised when you end craving. According to Buddha, death is not the end of craving for the majority of beings, you're reborn into a new realm/state. For example, 1 realm is the ghost realm where the consciousness hasn't given up the craving to leave the place they were hence why ghosts always seem to be seen where they lived/died. After some time, the fuel that burns the ghosts existence is exhausted and that consciousness is reborn into their new realm/state.
A human rebirth is generally considered a good rebirth because unlike animals, we have a chance to better ourselves and gain wisdom leading to the eventual cessation of craving, you end the cycle of rebirth which results in the ultimate peace you talk about. Anyway that's the theory, I'm far from that place haha
If you want to learn more, this is an excellent book. It doesn't mess about, it's dry, straight to the point.
www.amazon.com.au/Noble-Eightfold-Path-Way-Suffering/dp/192870607X?nodl=1&dplnkId=59c78ed5-e2d8-4d53-9ce4-2bab3fe55dcep.s I edited this because Remery sent me a PM worried fangman might be negatively effected through my choice of black humour. Fair enough. Cheers Remery.