Hello,
I use HA as a docker container as a sane person that I am 
so my problem is the UI. It has a lot of annoyances, you know little things that makes you crazy:
- on firefox you can not move entities up or down when you edit a card
- almost every time you click on history or logbook you get an error in the log, everything works but just knowing that error was generated in the log … crazy stuff ( :0:0 ResizeObserver loop completed with undelivered notifications. )
- nobody fixed the select box in a loong time, this happens on almost all select stuff I have (see image1 how I usually find it, and image2 how it should be)
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login is at least 2 steps back from everything modern, even my password manager dont know how to fill in sometimes, if you do not check Keep me logged in you can not do a refresh, if you do a refresh of the page you get logged out, don’t even keep the session open
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and last but most important, UI is kinda ugly, you can not do much with it without coding experience or without investing a lot of time into it
Those are my 2 cents!
