Unfortunately, I’m not familiar with installing Bitwarden so I can only offer general advice.
Port conflicts happen at runtime, not when software is installed. In general, you should be able to install as much software as you’d like that all relies on port 443 but only run one at a time.
If you’re seeing port conflicts when installing Bitwarden, then I suspect that something is starting the app after the install is done. If this is right, then maybe you can disable the automatic start. Or maybe you can ignore the error at install time, then configure the app, then start it.
I use proton vpn and Firefox Focus on iOS. I’m not sure which of them is doing the heavy lifting, but I rarely see ads on my phone.