Apple account 2FA makes accounted unable to access due to number not being mine’s and no one knows what the number is

When I started using Apple at a younger age, I used my dad’s Apple account on my phone which he had on his iPhone, which he barely used and had as a secondary one. At that time, I had gotten Minecraft purchased on it aswell another app that I had for free and it went paid. Throughout the years despite me making my own apple account, I still used that one for my App Store so I could access my paid apps, and I’ve also made in game purchases aswell as app subscriptions like Lightroom for a year. Bear in mind this is years since that account was made and I was still logging in no Two-Factor Authentication needed and my dad no longer has that account on any of his devices, which he’s switched to iPhone mainly now, a 15 Pro max and 12 Pro, but uses other accounts. I tried to download an app, Flight schedule pro, as I’m a student pilot, but it asked me to login which I did with the iCloud email and password, but then it sent a code to a number and asked for me to enter it, this number not being mine or any that I recognize, I go around asking my family members if they do recognize the number and no one does. I see the “can’t use this number” button aswell but it requires you to enter the whole number which no one knows about. I’ve read community posts and everyone says to start an account recovery but when I’ve tried it always asks for this phone number which I CANNOT provide. I really hope to get this resolved because I would like to download the app needed for my career and not have to use another account as I want to retain my purchases, subscriptions etc. I am also planning to get an iPad soon for piloting aswell as personal use in which I’d want to use this Apple account so I can access my Lightroom, games etc.