How to mount samba share on NAS at boot the same way it is mounted by "Files"?

Before you mark this as duplicate kindly read on.

I have a samba share on a NAS that is mounted only when I click on it in Files.

The share is mounted as

/run/user/1000/gvfs/smb-share:server=mycloudex2ultra.local,share=public

I would like the NAS to be mounted exactly like that, but at boot. What should I write in the /etc/fstab?

Instructions I have found are to mount the share in a directory under /media which is not what I am trying to do. Also, I don't know where the file with samba credentials is, if anywhere.

You can mount the smb share at boot by adding this line to /etc/fstab

//server/shared /path/to/mount cifs credentials=/path/to/creds.txt 0 0

For what your case seems to be:

//mycloudex2ultra.local/public /path/to/mount cifs credentials=/path/to/creds.txt 0 0

Also create a file /path/to/creds.txt and do chmod 600 /path/to/creds.txt with the following content:

username=Username
password=Password
domain=DomainName

You can read more through redhat's documentation here: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/managing_file_systems/index#mounting-an-smb-share-on-red-hat-enterprise-linux_managing-file-systems

The documentation would be very similar to Ubuntu

I really think you would be better off with a traditional CIFS mount as outlined by Killian Fortman's answer.

But if you absolutely need to have it mount like Nautilus does it then this example might work:

I created a file in my Ubuntu home directory: /home/tester/ServerCreds with this content:

guest
workgroup
dummypassword

I'm accessing a guest share that doesn't require credentials but gvfs demands I pass one anyway so I made something up.

Then go to Activities > Startup Applications > Add

Name: ServerPublicShare
Command:  bash -c 'gio mount smb://vxub2204.local/public < /home/tester/ServerCreds'

When I logoff and login again the share is mounted and available in Nautilus:

tester@vub2204:~$ ls -l /run/user/1000/gvfs
total 0
drwx------ 1 tester tester 0 Feb  7 06:56 'smb-share:server=vxub2204.local,share=public'