Urhg yeah well that sounds definitely related to the fact that you have a lot of domains … and in particular it’s probably the yunohost domain list calls taking some time because of uuuuh reasons that are too long to explain… (I’m guessing maybe you’re running a ‘slow’ hardware such as RPi or ARM board ? Maybe not idk)
Unfortunately there’s no quick immediate fix to address this … Could try to have a look to optimize the corresponding code