I currently only can get this working, if I flash it to the CH569
with gdb and openocd  over wch-link as follows:

1. Install openocd

$ git clone https://git.minori.work/Embedded_Projects/riscv-openocd-wch
$ cd riscv-openocd-wch
$ ./configure --enable-wlink  --prefix=/opt/riscv-openocd-wch --disable-werror --disable-jlink
$ make
$ sudo make install

2. In another shell go to mecrisp-quintus-0.37-experimental/mecrisp-quintus-source/ch569x

3. set ARMGNU to your installed riscv compiler:
$ export ARMGNU=riscv64-unknown-elf

4. build:
$ make

5. install wch-isp:
$ git clone https://github.com/hydrausb3/wch-isp
$ cd wch-isp
$ make
$ sudo make install
$ cd ..

6. Set debug mode on (you need to put the board in bootloader
   mode by connecting HD0 to GND while powering up the board):
$ wch-isp debug-on

7. Set the correct flash memory size (you need to put the board in bootloader
   mode by connecting HD0 to GND while powering up the board):
$ wch-isp flash64k

8. flash it:
./program.sh

this will flash the ELF file contents into the device flash.

The UART speed of the terminal on UART1 is set to 500000 baud by default.