The problem is that the Humax boxes were pretty slow when they were introduced - they weren't really powerful enough in my experience. I have the same with my Android TV (Philips) - it's really underpowered out of the box (I think it's a RAM issue). At least the EE Pro box seems to have a decent spec to do what it needs to.
I made the mistake of getting a TCL android TV and it's quite underpowered, so glad I have the pro box to use instead of the main TV OS as well as a fire stick.
However after the recent youview pro box software revamp it isn't as slick as it used to be. Probably again down to the hardware which is already 3-4 years old.
Handy to have another device like a fire stick if FAST channels are of interest then.
Totally get that the cost would outweigh the benefit. Having a background in finance, I get that logic.
However as the FAST channels are already on the mini box via the prime app, the apps are written with updated code I guess to support them.
Had no problems running the app on my G4 box.
Did have a time when the Android app did not work/kept crashing on my old Android 7 tablet so I had to resort to using the web version with the Chrome browser on that. Then the app started working again some months back. I am guessing that the new app will not even show as available to install on the old tablet so back to the web version again.
I really hope that my Android 13 phone is still supported (the web site is not specific on that) though I mostly use that for checking that the content I want is available before faffing around using a remote control to search for it. Can't remember the last time I actually watched anything on the phone.