Samsung Internet

[ToxicPoptart]

Why am I no longer able to change my default browser on my phone away from Samsung Internet?

[Mujibar]

I'm assuming you have another browser in addition to Samsung Internet installed on your device. If you're not able to select a different browser as default, have you tried resetting app preferences? Go to settings > apps > tap the 3 dots in the upper right.

[ToxicPoptart]

I do, I have Firefox. There is just no option to select a different browser

[Mujibar]

The option should be under settings > apps > choose default apps. If it's not there, reset app preferences as I described above.

Or set Firefox as default within Firefox itself, as @meself described.

[meself]

Check Firefox setting for set as default and uptick no need to set as preferred just use it

[nullandvoid]

You should just be able to go to your preferred browser, open the settings and set it as the default browser.  As a matter of fact, as soon as you open most browsers that are not your default, a pop up opens asking you to set it as your default.  If it does not, in Firefox, you can open the app, go to the settings, and the last item in the first section (general), is a toggle to set it as the default browser.  Once you set another browser as the default, it eliminates the current default. 

You can also go to settings, apps, choose default apps, and where it says "Browser app", tap that and then select the browser you want as your default.