Sharing connection between 2 RPi with Network Manager - raspberry-pi

Question

I have 2 RPis connected together with an ethernet cable. For the 1st RPi, the wifi is disabled, and it should get the internet connection from the 2nd RPi that is connected to the internet by wifi.
I am using the Network Manager (NM), and I also need that both RPis have static IPs on their eth0 interface:
RPi1 : 192.168.4.115/24 # The RPi that is not connected to wifi
RPi2 : 192.168.4.1/24 # The RPi that is connected to wifi
I configured the static IP of the RPi1 in /etc/dhcpcd.conf. For the RPi2, I used the NM when I configured the shared connection :
# On RPi2
nmcli connection add type ethernet ifname eth0 ipv4.method shared con-name local
nmcli connection modify local ipv4.addresses 192.168.4.1/24
nmcli connection up local
When I check the connection of the RPi2, I have the good IP, and when I ping 1.1.1.1 I have a reply:
pi#raspberrypi2:~ $ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.4.1 netmask 255.255.255.0 broadcast 192.168.4.255
inet6 fe80::514:af1e:da15:6f80 prefixlen 64 scopeid 0x20<link>
ether e4:5f:01:4c:5c:00 txqueuelen 1000 (Ethernet)
RX packets 105 bytes 20375 (19.8 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 178 bytes 22385 (21.8 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.11.16 netmask 255.255.255.0 broadcast 192.168.11.255
inet6 fe80::750f:5ec2:8158:fb80 prefixlen 64 scopeid 0x20<link>
ether e4:5f:01:4c:5c:01 txqueuelen 1000 (Ethernet)
RX packets 488 bytes 59706 (58.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 206 bytes 30178 (29.4 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
But on the first RPi, even if I have the good IP on eth0 (192.168.4.115), when I try a ping, I have connect: network is unreachable
So I don't know what is missing to achieve the sharing of the connection. And I don't know what I can check? Feel free to ask for any useful data, I don't know what can be useful.
The first RPi doesn't use the NM because I don't need it, the normal way of the RPi is enough.