Hi!
Just if it helps somehow, was getting the missing zicsr extension error at first when using the apt-installed riscv toolchain
```
pablo:~$ riscv64-unknown-elf-gcc --version
riscv64-unknown-elf-gcc (13.2.0-11ubuntu1+12) 13.2.0
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```
But then switched to using one pre-built by lowRISC
here, configuring $RISCV appropriately, and got everything working good without any -march changes.
```
pablo:~$ $RISCV/bin/riscv64-unknown-elf-gcc --version
riscv64-unknown-elf-gcc (crosstool-NG 1.26.0_rc1) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```
Seeing
this it seems that decoupling + extension was introduced around 2023.
Bests,
Pablo