Most computers should be able to run Nextcloud, but to double-check, look at the minimum requirements for Nextcloud. I run my instance using an old laptop I had lying around, and I think it has an 11th gen Intel processor of some kind and 8GB of RAM. It runs fine with plenty of headroom for many other services

If you’re only running nextcloud on it, any computer 15 years old or newer, with at least 4GB ram will be able to handle it.

If you want to have a reliable installation, avoid a raspberry pi and get a computer that can take at least two storage drives so that you can set up RAID. Or better yet, mount the storage from a dedicated NAS.