First, please post issues just once to prevent confusion from support personnel. Thunderbird is developing an app for smartphones but for now, it has not been released, so you need to pick from those email apps available. However, the beta version is available if you wish to join the beta group. More info here: https://blog.thunderbird.net/2023/09/thunderbird-for-android-k-9-mail-august-2023-progress-report/