Intel NUC - a great step up if you’re using your Pi for Home Automation (eg Home Assistant) and want something more robust/powerful. Likewise if you’re running PiHole or Docker. I have a NUC running VMware ESXI with Home Assistant, PiHole and a couple of other Docker containers and VMs. Most of these started on RPis but I decided I wanted something a bit more beefy. I also backup the VMs to my Synology using the Synology’s superb ESXi compatible backup software which is so good I tend to want to put everything in ESXi now and I’ll often create tiny Linux VMs for applications which I would previously have used a Pi for.
Arduino (or similar) - not strictly an alternative but a good step down in price and complexity for things that don’t need a full blown computer (simple robotics or home automation components/sensors).
Apple Pie - great if you don’t like raspberries. Fully wireless and nice with custard or ice cream.