Can't install age restricted apps; no age restrictions configured

For the last few years I have been able to install age restricted apps; iOS claims that I am not authorized, but in the settings I have no restrictions configured. I have tried setting restrictions + allow all, but does not work either. The problem has persisted across multiple devices and iOS versions, so I am sure this is very specific to my account and not a bug that many people have. I don't install many apps so I have just used this crippled OS like this, but now there is an app I NEED to install and it won't let me so after all these years I have decided to try to fix it.

Now, I think I know the reason for the problem but cannot fix it. Basically, many, many years ago (10?) I gave my old ipod to my children. The ipod had my account and I set up some restrictions. At the time, the restrictions were linked to the device, not the account. Some time later, Apple linked the restrictions to the account and my other devices stopped working properly. The problem is that that old ipod is lost and I cannot change its restrictions there. I can do it in my device, but like I said, I have ZERO restrictions on my current phone.

I hope some developer at iOS reads this because I don't think this is something that the community can help me with :-(

The only solution I have found online (a small number of other people seem to have this same problem) is to insall apps on iTunes and they will sync to the device. The problem is that I don't own a Windows or MacOS computer; only a Linux and a Chromebook and iTunes doesn't work there (I tried, with Wine; it is broken with the latest versions; some suggest using an older iTunes version but these files are not hosted by Apple but rather on a random Google Drive and installing that software would be a security hazard).