Hi,
I've been having this problem for quite a while: I can not change the default user interface leve. Basic is not enough 90% of the time and I'm tired of changing it constantly to a higher level. Supposedly, I should be able to change that.
I though it might have been something getting hosed up on my configuration, but recently I had a hard drive failure and needed to re-install tvheadend. The issue persists in 4.2.5-2 and also in 4.3.r912.g5fe3ebd48-1 (I'm using Arch and it's AUR ebuilds).
I'm trying to change the user interface level in the general settings and also per-user, but none have effect (althouh the setting is saved).
Also, setting "persistent interface level" will essentially lock one out of changing the level, since the only way to actually change it that will work is next to the help button.