redundant-open-modes (UP015) only recognizes seven redundant modes in Ruff 0.7.3:

However, many other modes are redundant. t and U can always be omitted. r is redundant unless b or + is present. The characters can appear in any order; although the rule handles wt, for example, it misses tw.

More information:

• Python documentation: https://docs.python.org/3.10/library/functions.html#open
• CPython source: https://github.com/python/cpython/blob/v3.10.0/Modules/_io/_iomodule.c#L273
• Full lists of modes: https://github.com/python/typeshed/blob/ea368c72696afba1eb4c12653123edd764c800bf/stdlib/_typeshed/__init__.pyi#L178