Backports to release v1.12

[dkarrasch]

• Fix opnorm for banded matrices #1428

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.59%. Comparing base (7f4b476) to head (aefcbfa).
⚠️ Report is 1 commits behind head on release-1.12.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.12    #1429      +/-   ##
================================================
+ Coverage         93.56%   93.59%   +0.03%     
================================================
  Files                34       34              
  Lines             15474    15476       +2     
================================================
+ Hits              14478    14485       +7     
+ Misses              996      991       -5     

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