Time Capsule replacement

AFAIK, no one has yet perfected a Time Capsule replacement that will meet your requirement of "just let it work." However, a few Asus and Synology models do show promise in that regards, but time will tell if they offer consistent backup performance and stability.

Most testing does not run long enough so when you see articles saying some router has Time Machine extensions be dubious as things appear very different in long term testing.

In my testing the Asus worked ok.. but would corrupt the TM backup on average every 2months. This is somewhat more often than to a Time Capsule.. between 6-12months on the same computer. Time Machine not being particularly great of late. I did not have a chance to try to Carbon Copy Cloner as alternative but that is what I would try.

Synology I tested for shorter time but it worked better.. The firmware of the Synology router is heavily based on the NAS which does work really well.

Both Tesserax and I use Synology NAS which does work very reliably.

If you are prepared to spend the extra a NAS can be well worth the extra expense especially if you can use it as file server and media server to your network.

Portable USB drives tend to be a mixed bag. So be careful as some do not work particularly well. In general desktop drives are more reliable than cheap end laptop drives.

Note also if you expect the USB port of the router to provide power .. check the specs for exact current capability of the port since most routers only have a small power supply.

Any hard disk plugged directly into USB of the computer works much better than over network. Time Machine uses a somewhat different method to backup which are not compatible.

We do generally recommend using local hard disk if you still want Time Machine to work reliably on later OS (since Sierra).

It’s not a modem but I purchased a 2 Tb backup by Seagate. Has worked perfectly for the last five years and can be accessed from Time Machine app.