Same issue with me.
Roku 4 ultra and Real Time with Bill Maher via HBO Max.
Playing any episode will crash the application. There's a very brief (less than a second) message that appears before getting punted back to the home screen.
Other titles on HBO Max play just fine, but Real Time content is definitely not available via the Roku platform (show plays just fine on PC, phone, etc.).
I've uninstalled the channel, restarted the roku, etc., etc. No difference.
My cable Co. Is constantly begging me to use their 4K streaming device (comes with the internet package), and to date, I've not even considered it before. That is no longer the case.