Have you tested whether you can sideload APKs with any of the alternative file managers (e.g. Google's "Files" app) that you've installed? There's a good chance that adding 3rd party file manager apps won't help since app installation privilege is most likely restricted to a specific android package ID (like "com.android.documentsui") and signing key and only the "factory" Files app is on this "whitelist". Even if for some reason your current OS version doesn't contain such a restriction (which is possible, but would be odd), after the update to the new OS version it might be restricted.
Have you tested whether you can sideload APKs with any of the alternative file managers (e.g. Google's "Files" app) that you've installed? There's a good chance that adding 3rd party file manager apps won't help since app installation privilege is most likely restricted to a specific android package ID (like "com.android.documentsui") and signing key and only the "factory" Files app is on this "whitelist". Even if for some reason your current OS version doesn't contain such a restriction (which is possible, but would be odd), after the update to the new OS version it might be restricted.
I can it works. I download directly to the car and open from dl folder too. They won't take the cars folders away