A simple, lightweight LibDataBroker plugin which allows you to switch talent loadouts.
This requires a display addon like TitanPanel, ChocolateBar, or ElvUI etc to function. You will have to configure the display addon to show this plugin.
You can configure the text that shows up yourself, in the config (/talentloadoutbroker or /tlb to open it).
Blizzard doesn't always play nice, and sometimes likes to bug out their own talent UI. This DataBroker plugin should still consistently show the correct loadout however, even when blizzard's own UI bugs out :)