On Xiaomi Mi Note 10 I can't clean the caches of apps.
A workaround for cleaning the caches that worked partially was to make the Google PlayStore display the warning about missing disk space for an app update (by filling all available disk space) and clicking "Zum Speicherplatz" (go to disk space) then clicking on "Data in cache" to delete that cache. However, that does not delete all the app caches, only what is detected by the playstore and cache-cleaning apps don't work at all.
When I try deleting the app caches with a cleaning app, it runs without an error but no disk space is actually freed up afterwards. Also it displays that lots of system app each have a cache of the same size (for example 50 MB each and 1 GB overall) and doesn't display the actual apps with large caches, but this may vary. It does not run without an error with the cleaning app "1 tap cleaner" which doesn't work at all because the buttons are greyed out when it tries doing the below automatically.
When I go to manage apps and open an app there, the "delete data" (and the "force quit") button(s) are disabled (greyed out) and "disk space" displays "0,00 B". On a previous phone the same apps also had a lot of data in the cache but I could always delete them manually and with cache cleaning apps.
Here's how I know that the caches of some apps are larger and that they haven't been deleted (beyond that there should be more disk space left): there's a stock app "Deep cleansing" ("Tiefenreinigung") and it shows which apps take up a lot of disk space (when clicking on "Apps" on the page). The buttons for the apps are also greyed out for but I could delete their large caches on another Android phone. Screenshots:
An app taking up a lot of storage space with its cache that is not shown in the first screenshot is the stock Gallery app by Mi UI which can't be deinstalled and also has the delete data button greyed out. At least that what a scan with SD Maid shows.
When I go to "Deep cleansing" ("Tiefenreinigung") app data at the bottom only shows <10 MB that it could remove.
The phone has the latest updates but I generally decline any prompts it shows for giving some permissions to private data (however it may be that I once accidentally pressed allow when installing an app because I think it used to show two prompts asking for private data permissions after installing any app but now it shows only one; if there's a way to check and revoke let me know). I'm having this problem for quite a while now.
I don't know why it's legally allowed to prevent users to maintain usable phones and be able to delete their caches.
Do other users of that phone have the same problem? So far the only thing I could find was comments here which suggests few other users also experience this.
What's causing this problem and what else to try?