Would you be interested in working on matrix factorizations and triangular solvers? When I first introduced the iterative solvers, I had included LDL^t factorizations and triangular solve for dense and CSR sparse matrices to be used as preconditioner. But then removed it to make the PR easier and also because this part needed some more thoughts on the general API in order to be used standalone or with other solvers.
@loiseaujc opened an interesting topic about derived types for handling matrix factorizations, i think this could part of a larger idea to abstract away array manipulations.
Another topic that would be interesting would be to enable with c-preprocessing to use either MKL or NVPL for some sparse matrix operations as drop-in replacement if one links against those libraries.
Just some food for thought.
BTW, in case you don’t know, you can play around with stdlib on compiler explorer Stdlib in Compiler Explorer I use it a lot as a nice playground.