Below is the "hardware requirements" section from their github page.
**Hardware requirements** Dendrite in Monolith + SQLite works in a range of environments including iOS and in-browser via WASM. For small homeserver installations joined on ~10s rooms on matrix.org with ~100s of users in those rooms, including some encrypted rooms: Memory: uses around 100MB of RAM, with peaks at around 200MB. Disk space: After a few months of usage, the database grew to around 2GB (in Monolith mode). CPU: Brief spikes when processing events, typically idles at 1% CPU. This means Dendrite should comfortably work on things like Raspberry Pis.