Is there a trial license for 11.5.4

Talk to your F5 account manager or reseller they should be able to get a 30 or 45 day trial license for you.

90 day trial can be requested here - https://www.f5.com/trial/big-ip-ltm-virtual-edition.php

90 Days trail can only be used for Version 11.3.0 and not Version 11.5.4

I downloaded 11.5.3 used the trial license and then upgraded it to 11.5.4

There's a lab license too for $99 i believe.