That's the wrong source, please read the error message carefully - the solaar ppa for which the error occurs does not provide any bionic packages.
** Changed in: apt (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1831025 Title: apt update fails with ` 404 Not Found [IP: 91.189.95.83 80]`. Possible cause: three dots in the sources.list To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/1831025/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs