I upgraded two production systems and one test system from 4.2.3 to 4.3.
No hick-ups, everything running as expected. 
The log viewer works fine for me (direct connection, browser).
Additionally, I deployed my self-built add-on (5.0.0-SNAPSHOT) to both a 64-bit Java 21 system and a 32-bit Java 17 system as described here. Also running fine - as far as I can tell!