I’m using DeltaChat in July 2024 and it constantly nagged me about a Update Available popup. Could you please just let user decide and continue using what they want!? Your app is much like Firefox who took away the ability to choose whether to check|apply an update or not.
DISABLING UPDATE SHOULD BE THE USER’S CHOICE, NOT YOURS!!!
first of all, welcome aboard - and greetings to the future
not sure, about the versions we ship in the future in July 2024 (here is still May 2023), however, current versions show a first reminder after one year and then every month only. the reminders are not shown as a popup but as a non-instrusive device message 
regarding the drawbacks of not updating, and that these drawbacks may also affect people you write to, this frequency was regarded as a good compromise. also, other than some other apps, you can still chose to ignore these reminders, which, however, is not recommended at all
Delta Chat actually does not check for updates, but adds a device message once the integrated provider database is 1 year old. There is no connection to some update server involved in this, the check is completely offline.