What can replace Apple Time Capsule?

What is the best replacement for Apple Time Capsule?

In truth, there really is no direct replacement for a Time Capsule, so finding a "best" replacement is going to be quite a challenge.

Remember that a Time Capsule was really two products in one. It was a WiFi router with a built in hard drive in the same physical package or enclosure. No other manufacturer ever offered the same type of product, so there is really no direct replacement at all for a Time Capsule.

The closest that you can come to a Time Capsule at this point is a router from Synology or Asus that includes a USB port that will support Time Machine backups to an attached USB hard drive. So, two separate products that work together instead of one.

If you don't really need another WiFi router, you might want to take a look at a product called a Network Attached Storage device or NAS for short. Synology is a popular choice among regular contributors to this support forum.

The simplest, cheapest, and most reliable solution is simply connect a USB hard drive directly to your Mac and back up that way. That just might be "best" for a significant number of users.

“Best” is something only you get determine, and you’ll want to create a list of what you want, what you need, what you don’t, and your budget. Details here include Wi-Fi 5, Wi-Fi 6, how much storage you need, and other details. There are comparatively few devices that combine both Wi-Fi and network storage, Synology makes two, though you’ll need to add USB storage with those. There are various (many) options with separate Wi-Fi and NAS storage, Synology makes a bunch of NAS options with Time Machine support, and Synology, Ubiquiti, and other vendors offer Wi-Fi access points or Wi-Fi routers.