Cannot install Brave on Linux Ubuntu due to "curl: (6) Could not resolve host: brave-browser-apt-release.s3.brave.com"

First, here’s the whole history of what happened in the terminal as I tried to install Brave on my Linux Ubuntu system:

Terminal History
joseph-slade@head-honcho:~$ sudo apt install curl
[sudo] password for joseph-slade: 
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
curl is already the newest version (8.2.1-1ubuntu3.3).
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
joseph-slade@head-honcho:~$ sudo curl -fsSLo /usr/share/keyrings/brave-browser-archive-keyring.gpg https://brave-browser-apt-release.s3.brave.com/brave-browser-archive-keyring.gpg
curl: (6) Could not resolve host: brave-browser-apt-release.s3.brave.com
joseph-slade@head-honcho:~$ echo "deb [signed-by=/usr/share/keyrings/brave-browser-archive-keyring.gpg] https://brave-browser-apt-release.s3.brave.com/ stable main"|sudo tee /etc/apt/sources.list.d/brave-browser-release.list
deb [signed-by=/usr/share/keyrings/brave-browser-archive-keyring.gpg] https://brave-browser-apt-release.s3.brave.com/ stable main
joseph-slade@head-honcho:~$ sudo apt update
Hit:1 https://ppa.launchpadcontent.net/openshot.developers/ppa/ubuntu mantic InRelease
Ign:2 https://proget.makedeb.org prebuilt-mpr InRelease                        
Hit:3 http://us.archive.ubuntu.com/ubuntu mantic InRelease                     
Hit:4 http://us.archive.ubuntu.com/ubuntu mantic-updates InRelease             
Hit:5 http://us.archive.ubuntu.com/ubuntu mantic-backports InRelease           
Ign:6 https://brave-browser-apt-release.s3.brave.com stable InRelease          
Hit:7 https://repo.steampowered.com/steam stable InRelease                     
Ign:8 http://security.ubuntu.com/ubuntu mantic-security InRelease              
Hit:8 http://security.ubuntu.com/ubuntu mantic-security InRelease              
Ign:6 https://brave-browser-apt-release.s3.brave.com stable InRelease          
Get:6 https://brave-browser-apt-release.s3.brave.com stable InRelease [7,547 B]
Err:6 https://brave-browser-apt-release.s3.brave.com stable InRelease   
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0686B78420038257
Ign:2 https://proget.makedeb.org prebuilt-mpr InRelease
Ign:2 https://proget.makedeb.org prebuilt-mpr InRelease
Get:9 https://proget.makedeb.org prebuilt-mpr Release [9,672 B]
Reading package lists... Done      
W: GPG error: https://brave-browser-apt-release.s3.brave.com stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0686B78420038257
E: The repository 'https://brave-browser-apt-release.s3.brave.com stable InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Skipping acquire of configured file 'mantic/binary-i386/Packages' as repository 'https://proget.makedeb.org prebuilt-mpr InRelease' doesn't support architecture 'i386'
joseph-slade@head-honcho:~$ sudo apt install brave-browser
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package brave-browser
joseph-slade@head-honcho:~$ sudo curl -fsSLo /usr/share/keyrings/brave-browser-archive-keyring.gpg https://brave-browser-apt-release.s3.brave.com/brave-browser-archive-keyring.gpg
curl: (6) Could not resolve host: brave-browser-apt-release.s3.brave.com
joseph-slade@head-honcho:~$ 

Keep in mind that this doesn’t include the moments where (IIRC) three components were deleted, where I assumed this would resolve the issue, which made no difference, hence why they’re not shown in the terminal history. In addition, this was not my first attempt, but my second one, just to make sure there was no human error on my part, and (again, IIRC) I’ve since lost the history to the first attempt, so I will unfortunately not be able to show that in the post.
That alone was enough for me to have to come to the Brave community for help, and I usually don’t seek help immediately after running into trouble, but this was already indicating deeper issues with the installation process that I knew I couldn’t fix by myself.
Now, here’s the exact error where everything went downhill—and I knew I was stuck:

curl: (6) Could not resolve host: brave-browser-apt-release.s3.brave.com

Now, this seems to indicate server and internet issues I don’t understand yet, plus the fact that this post doesn’t have the “linux” tag since I don’t quite know how to use the site yet, and on behalf of the rest of the techies in the world, I apologize if I sound stupid.
That being said, I literally don’t know where else to go, nor what else to say about this issue. If you have any advice or solution or are willing to give me any at all, please do so as soon as you are able. Thank you so much for the help and support.