When in doubt, stick with the firmware you have. A stable, outdated router is safer than a bricked one from a bad update.
The search results for "DSL-3890 firmware link" are a minefield. dsl3890 firmware link
Unplug the power cable for 30 seconds. Hold down the recessed Reset button on the back of the device using a paperclip, plug the power cable back in while continuing to hold the button for 10 seconds, and release. This should trigger the router's emergency recovery mode interface at 192.168.1.1 , allowing you to attempt the upload again. The Firmware File Format is "Not Recognized" When in doubt, stick with the firmware you have
Protects against vulnerabilities like WPA2 exploits or unauthorized remote access. Unplug the power cable for 30 seconds
The "story" of the DSL-3890 firmware link is not a simple tale of a download button. It is a drama of internet service providers (ISPs), locked-down hardware, and the eternal struggle between corporate security policies and the end-user’s desire for control.