Your issue is not a basic issue with Manjaro - but a local network configuration.
Such issue is is next to impossible to troubleshoot remotely.
The first step is to restart your router and thus the dns service.
Undo/Revert any customization you may have made in networkmanager.
/etc/resolv.conf is controlled by the resolvconf program and written by NetworkManager.
You can control resolvconf using the /etc/resolvconf.conf file to set a specific nameserver - and this is great for troubleshooting. It is highly recommended to locate the actual issue interfering with setting a nameserver
/etc/resolvconf.conf
name_servers 8.8.8.8
run resolvconf to update the resolv.conf
sudo resolvconf -u
then reset your network (from your inxi the eno1 is your nic)
sudo ip link set eno1 down
sudo ip link set eno1 up
systemd-resolved
In some situations it may help to remove openresolv package and enable systemd-resolved.service.
sudo pacman -R openresolv
sudo systemctl enable --now systemd-resolved.service