Depends on your needs. Matrix can mostly replace the functionality of Discord, which makes it stand out despite its flaws.
If you just need group chat, encryption, and 1 on 1 calls, XMPP is easily self hosted and highly scalable.
SimpleX seems to be another decent option that’s decentralized.
For those needs, an old used thinkpad off ebay would be pretty ideal. Affordable, well built and reliable. Only downside is I think the smallest model is a 12"
Perhaps a Chromebook known for being compatible with being flashed with Linux?