Comment (by Roland Haas):

I have added FLRWSolver to the main ET thornlist as:

# FLRW cosmological initial data
!TARGET   = $ARR
!TYPE     = git
!URL      = https://github.com/hayleyjm/FLRWSolver_public
!REPO_PATH = ../$2_public
!CHECKOUT =
FLRWSolver/FLRWSolver

which checks out FLRWSolver_public and creates a thorn FLRWSolver/FLRWSolver for it.

If you would rather use a different arrangement or thorn name, please let me know.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2549/inlcude-flrwsolver-in-et