[adament]

Would you care to elaborate which device it is? 12 years old means it at the most could have come with Honeycomb when you bought it. Has the base OS been updated since? It is great that you bought a device which presumably got OS updates for many years, unfortunately that is not common for android devices. And the problem is, if it did not get an OS update, the truststore did not get updated, and thus it does not trust the LetsEncrypt root CA sometime next year. Except for Firefox which luckily comes with its own root certificate list.

Iphone 7 got an iOS update to 15.7.7 in 2023 and its truststore contains the ISRG Root X1 certificate: https://support.apple.com/en-gb/HT212773 I am unsure which apps you cannot install but a quick look in the app store indicates that Zoom, LinkedIn, Notability, 1Password, Disney+ and Netflix all support iOS 15.7. And in my anecdotal experience I could find no app with a minimum OS requirement greater than 15.7. As far as I can tell you need to go back to iPhone 4S to find an iphone which does not support the LetsEncrypt root certificate. That device is only 11 years old, so still worse than your Android device. And I do not think there is a workaround by using a different browser like for Android.

[hhh]

My grandmother has a Google TV, still works with a bit of stuff. Running Honeycomb.