The Guacamole version for HTML5 session is 0.9.9 released in january 2016 ! The current version of Guacamole is 1.3.0 released in 1 january 2021. Why Pulse doesn't upgrade Guacamole ? Because there is a known issue with keypad inactive due to Num. Lock activation failed at launch.
This KB is talking about the subject since 2017 :
What kind of difficulties encountered Pulse to upgrade Guacamole ?