Comment 23 for bug 1821630

Ok. It's interesting to see that you have two other vendor keys in your DB:

        Issuer: CN = Inventec BU2
        Validity
            Not Before: Jun 14 16:00:00 2012 GMT
            Not After : Jun 14 16:00:00 2022 GMT
        Subject: CN = Inventec BU2
[...]

        Issuer: C = JP, ST = Tokyo, L = Ome, O = Toshiba Corporation, CN = Toshiba Corporation Utility CA 2012
        Validity
            Not Before: Aug 10 06:15:36 2012 GMT
            Not After : Aug 10 06:15:35 2027 GMT
        Subject: C = JP, ST = Tokyo, L = Ome, O = Toshiba Corporation, CN = Toshiba Corporation Utility CA 2012

However, in addition to these you also have the standard expected Microsoft CA:

        Issuer: C = US, ST = Washington, L = Redmond, O = Microsoft Corporation, CN = Microsoft Root Certificate Authority 2010
        Validity
            Not Before: Oct 19 18:41:42 2011 GMT
            Not After : Oct 19 18:51:42 2026 GMT
        Subject: C = US, ST = Washington, L = Redmond, O = Microsoft Corporation, CN = Microsoft Windows Production PCA 2011

So I'm afraid this still doesn't give me any clue as to why your system won't boot Ubuntu under SecureBoot.

What is the output of 'mokutil --dbx' on this system?