I also love my Oneplus 7 Pro, currently running crDroid (on Android 13, based on Lineage). It is updated semi-weekly and maintained by one person. It gets the latest security updates, but I am unable to relock the bootloader, if that is relevant to your threat model.
I’m probably going to do a battery swap soon and really want to use this phone until it breaks!
You could actually still use this (on Android), because you can visit Reddit in the browser, and Firefox allows you to use an addon called “Tampermonkey”.
But then I don’t know if the json file would be of any use to you, probably not :/
If you only need json, I recently wrote a userscript that exports saved posts and comments for myself. Please report back if it works/you decide to use it :)
(It works by scraping the pages, so its gonna take some time) (It also has horrible ui, sorry) https://github.com/hyperacuity/userscripts
I do not use Google Pay or Netflix on my phone, and my german banking apps work perfectly fine. YMMV though