I see myself doing this when older. For now I am annoyed by social networks but a smartphone is good when traveling and for communication from abroad, so what I do is I do not put anything other on it just couple communications apps like signal, organic maps and thats pretty much it. No urge to check it 100x a day, only when needed so it stays in the bag most of the time.
Its a dumb phone, you insert a sim card and thats it. The telco will know where you are based on the sim connection to towers (as with any other phones) and all calls and texts are stored, but other than than you dont have to worry about anything else. I suppose you dont have to login to some account to make it work therefore even if it harvests any data, it does not know who it belongs to (no add ID) so not saleable. Its pretty easy, no real identity (through email, account, etc) attached to it = private.
I find ryanair much more reliable than say Wizzair, who seems to be late everytime I use them, sometimes even hours. I think Ryanair strategy is to sell you a 20 euro ticket, and then get more money out of you by all kinds of moves. So if you have a bit of experience you can fly cheaply, if not, you will learn and pay more.
The thing is that today you dont even need access to the coversation when you have metadata. Imagine, a woman calls a number of center for planned parenthood, is on the phone for 20 mins. Then she calls a number of her gyno doc for couple mins. Then her phone is located at that gyno doc a week later for 2 hours or whatever it takes. Do you need to decrypt the conversation? You already know what was discussed.
Its most probably not that X has access to your phone. I believe since some older version of android, all apps are sandboxed and there are rules to what they have access to (Android Run Time, SELinux). How this works IMHO is you are using a normie (google) android phone. You have an advertising ID assigned to it (you can find it in the setting under Privacy/Marketing), which is visible to apps, therefore the Feeder app sees it and sells the data of what you are looking at tied to the ID, someone buying it for a campaign on an exchange and uses it for marketing on X, which shows it to you based on that same advertising ID because it can see it also. To avoid 95% of tracking like this, use a degoogled android phone. In case you use iPhone, there is nothing you can do.
Do you really not have prepaid sim cards in the US? that you buy with 5 bucks and it lasts one year, and then you just top it up for another 5? Those carriers are really milking you good over there.