In v2.38.0 (31955475d1c283120d5d84247eb3fd55d9f5fdd9)
"submodule--helper --list" was remove because

We're not getting anything useful from the "list | cut -f2"
invocation that we couldn't get from "foreach 'echo $sm_path'".

But we get speed (this is with about one hundred modules):

$ time git submodule foreach -q 'echo $sm_path' > /dev/null

real    0m0.585s
user    0m0.413s
sys     0m0.182s

$ time git submodule--helper list > /dev/null

real    0m0.008s
user    0m0.004s
sys     0m0.004s

Please consider restoring this subcommand or providing something
equivalent that is just as fast.

     Thanks,
     Jonas