Multiple Problems when trying to update Ubuntu

So I'm currently in the process of upgrading from 22.04 to 24.04.1 LTS for a laptop and I'm running into multiple problems, but here's what happened first

I tried to update Ubuntu using the software updater but it gave me this error messages:

"Failed to download repository information, check your internet connection"

Then after I clicked OK it gave me this message:

"The software on this computer is up to date.""However, Ubuntu 24.04.1 LTS is now available (you have 22.04)"

Then it showed me the release notes and I clicked upgrade again, the "distribution upgrade" window showed and it got a decent way through the "setting new software channels" section before it showed me this message

W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., W:An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://repo.protonvpn.com/debian stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8DD48989F43719CA, E:The repository 'https://example.com/apt stable Release' does not have a Release file.

I've tried dealing with the no public key error and the example.com error so I'll talk about what I've done for them separately

For the public key error, I tried following the top answer on this "https://askubuntu.com/questions/13065/how-do-i-fix-the-gpg-error-no-pubkey" post, which led me to type this into the terminal

sudo mkdir -m 0755 -p /etc/apt/keyrings/curl -fsSL https://example.com/EXAMPLE.gpg |    sudo gpg --dearmor -o /etc/apt/keyrings/EXAMPLE.gpgecho "deb [signed-by=/etc/apt/keyrings/EXAMPLE.gpg] https://example.com/apt stable main" |    sudo tee /etc/apt/sources.list.d/EXAMPLE.list > /dev/null

I'm pretty sure this is what created the example.com does not have a Release file" problem but I'll continue

After that didn't work I just tried to fully delete proton VPN so I entered these commands from their website

sudo apt autoremove proton-vpn-gnome-desktop && sudo apt purge protonvpn-stable-release

After that didn't work I tried using its instructions for removing the old version

sudo apt-get autoremove protonvpnrm -rf ~/.cache/protonvpnrm -rf ~/.config/protonvpn

And as far as I could tell that successfully deleted proton vpn but I'm still getting the no public key error when I try to update (I sadly don't have the output from when I originally did this (I closed the terminal window) but here's the output from when I did it again)

Reading package lists... DoneBuilding dependency tree... DoneReading state information... DonePackage 'protonvpn' is not installed, so not removed0 to upgrade, 0 to newly install, 0 to remove and 3 not to upgrade.

And for the "E:The repository 'https://example.com/apt stable Release' does not have a Release file." error, I believe I accidentally created it after following this [solution](How do I fix the GPG error "NO_PUBKEY"? posts instructions)

So my question is how do I fix this?, I assume I have to delete some files for example.com and proton vpn but I don't know how to do that

(also I'd prefer not to have to do a fresh install but if you think I should, I probably will)