As the current stable version 3.3 of Hamlib does not support the IC-9700 you need to download and install a daily snapshot of the master development branch or clone it from github and compile by yourself. https://hamlib.github.io/

I took the second option. You'll need to have some development tools installed, e.g. build-essential in Ubuntu.
Brief description:

git clone https://github.com/Hamlib/Hamlib.git
cd Hamlib
autoreconf -i
autoconf
./configure
make check
make install

If everything works fine,

$ rigctl --version
rigctl(d), Hamlib 4.0~git
Copyright (C) 2000-2012 Stephane Fillod
Copyright (C) 2000-2003 Frank Singleton
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

will bring up the new version. You'll probably need to restart cqrlog.

To avoid changing USB Port numbers, it is recommended to add some udev rules. The IC-9700 has two USB-to-serial ports,
unfortunately it's linked to the serial number of your radio.

If someone like to use this rule, please replace 'nnnn' with your serial number. Find out with

sudo lsusb -vd 10c4:ea60 | grep iSerial
sudo lsusb -vd 10c4:ea60 | grep iProduct


This is how my /etc/udev/rules.d/92-persistent-usb.rules looks like:

#IC-9700
ACTION=="add", SUBSYSTEMS=="usb", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60" , ATTRS{product}=="CP2102N USB to UART Bridge Controller", ATTRS{serial}=="IC-9700 nnnnn A", SYMLINK+="radio_ic9700a"
ACTION=="add", SUBSYSTEMS=="usb", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60" , ATTRS{product}=="CP2102N USB to UART Bridge Controller", ATTRS{serial}=="IC-9700 nnnnn B", SYMLINK+="radio_ic9700b"


Sample config for remote control IC-9700:

cqrlog preferences TRX control
RIG model: 381 Icom IC-9700
Device: /dev/radio_ic9700a /* this should be ICOMs USB1 (A) Port */
Serial Speed: 57600, DTR OFF, RTS OFF

ICOM IC-9700 Set > Connectors > CI-V
CI-V USB Port: Unlink from [REMOTE]
CI-V USB Baud Rate: 57600
CI-V USB Echo Back: ON

Finally, I modified the default frequencies, as 23cm was missing (Preferences -> TRX Control -> Change default frequencies.
So far, I didn't find out, how to add a frequency or a mode. As I'm not on 6m, I used this slot for 23cm.

73, Rolf