Networkmanger should pull the DNS server from the access point to which you are connected and append it into resolv.conf as
nameserver 0.0.0.0
Where 0.0.0.0 is the ip address of the DNS server that was retrieved from the access point.
A dirty way to fix it without figuring out why that isn’t happening is to manually set the nameserver and set the resolv.conf file to be immutable by adding the +i bit to the file.
$ sudo chattr +i /etc/resolv.conf
A better solution may be to just check in settings, open the WiFi settings for your access point or the ethernet interface settings and check if the DNS is set to be obtained automatically from the router.
If you run dnscrypt-proxy on your laptop then manually configuring the resolv.conf file to have 127.0.0.1 as the nameserver and setting the immutable bit works to prevent networkmanager from changing it when the network status changes.
The network interface names have changed with udev, eth0 and wlan0 were from old naming conventions.
This has been this way a pretty long time now.
With the new naming convention eno0 is probably your ethernet (RJ45) port and wls6 is your WiFi.
You can add
net.ifnames=0
To your kernel command line to revert to the old naming convention (eth0, wlan0, etc.)