On two Mint 18.3 XFCE computers all my Windows network computersshow up in Thunar under Network and I can access them whether Windows XP or Windows 10.
On Mint 19 XFCE 64 nothing shows up.
I followed the steps in HowTo: Samba Browsing Problems Checklist viewtopic.php?f=42&t=88146&start=0
 - yes same subnet
sudo service smbdand s
udo service nmbd. The response indicated that Samba was not installed at all so I installed it. Then using software manager I compared which components were installed on 18.3 and 18 and it looked like the same packages in both 18 and 19.
 - hostname obviously no problem since network computers show up on 18.3
 - there is no name resolve order line in smb.conf in the working 18.3 or in 19
 - ufw is off in Mint. Firewall on Windows machines not blocking since i can access from Mint 18.3 (and other Windows).
 - workgroup = WORKGROUP
Next I looked at Mint 19 and Samba File Sharing Changes viewtopic.php?f=42&t=270442
Mint 19 as a Samba Client
client max protocol = NT1did nothing.
after I did all the above
smbtreeshows all the shares but nothing shows up in Thunar file manager Network except the computer I ran the command on.
About a day after I wrote this, Thunar on Mint 18.3 also stopped seeing Windows network computers.
The next day just for the heck of it I tried adding
client max protocol = NT1to the Mint 19 PC and it worked this time. By the way, this includes seeing and being able to access a Windows 10 share, contrary to what Mint 19 and Samba File Sharing Changes viewtopic.php?f=42&t=270442 says. One thing I had done in the interim is reboot the 18.3 to Vista to run some Windows-only program. So I booted it back to Mint and still no Windows shares in Thunar. So just for the heck of it I booted it back to Vista again and found that Vista couldn't see the network shares either.
One other piece of information is that all this time I had my old trusty XP computer running. It never goes to sleep. So I assume it remains the Master Browser. There is also a Win10 PC on the network. It does go to sleep.
So it appears that there is more to this problem than just the Mint 18-19 samba/cifs configuration.
Any networking experts out there?