Quick and easy: read the docs and even if it says, “Low impact,” double-check that you aren’t going to run into problems.

Here is a link to upgrade document with quick fix: Laravel 9 Upgrade Guide.

The Trusted Proxy code wasn’t even something on my radar. I saw it as a Middleware and moved on with my life. Luckily, the Laravel team already caught this in their testing and the fix was quick and painless. Laravel 9 engaged 🏄‍♂️.