Separate from the enhancements in #9269, I wanted to keep a list of deferred maintenance.

• copy linprog documentation descriptions into method-specific documentation (e.g. https://docs.scipy.org/doc/scipy/reference/optimize.linprog-interior-point.html) (ENH: optimize: add HiGHS methods to linprog - continued #12043)
• address two little comments in ENH: optimize: interpolative decomposition redundancy removal for linprog #11249 (see comment here)
• add highs method-specific option tests (see comment here)
• rename _T_o in linprog and all linprog methods, perhaps to _postsolve_args if that makes sense. Document it everywhere.
• Document **unknown_options (DOC: Add missing docs for linprog unknown_options #10099)
• clean _clean_inputs. Several have commented that it is too messy. (Clean _clean_inputs in optimize.linprog #10083)
• figure out what changes caused interior-point to report failure despite success on some Netlib benchmarks (BUG: optimize: tweaked linprog status 4 error message #10025)
• "We're often passing c, A_ub, b_ub, A_eq, b_eq, bounds, x0 between functions. Maybe this should be refactored into a container e.g. a namedtuple or dictionary?" - @Kai-Striega. Update: Done in MAINT: optimize: refactor common linprog arguments into namedtuple #10602.
• sym_pos=True to assume_a='pos'
• Simplify control over method='interior-point' solver: one option solver instead of separate boolean options cholesky, sym_pos, and lstsqr
• change bounds to NumPy arrays internally. Ensure that _check_result checks solution against original bounds.
• allow bounds to be specified as NumPy arrays
• allow bounds to be specified as Bounds objects (A 6 x 6 linprog testcase: 3 methods x sparse / dense give different results #10288)
• automatically remove constraints with infinite upper bound (A 6 x 6 linprog testcase: 3 methods x sparse / dense give different results #10288)
• loosen tolerance for linprog(method='simplex') as mentioned in ENH: linprog in SciPy 1.2+ discussion #9269
• add stacklevel argument to warnings
• _check_result should have relative tolerance
• clean up interior point display issues - see TST: optimize: fixed linprog "disp": True bug #10498. Why exactly is alpha sometimes an int? An array with one element? Fix at the source. Ensure that arguments to _get_step are always floats (not single-element arrays), and change 1 in _get_step to 1.0.
• expose control of conceptually distinct tolerances to user. (For instance, tolerance for pivot selection should be distinct from the tolerance for constraint satisfaction checks.)
• Revisit excepts with generic Exceptions (ENH: optimize: dense redundancy removal routine optimizations #11245)