I was able to change the TTL by editing the TTL file in android file system. I don't remember exactly where the file was located but I'm thinking it was inside of the /proc/sys/net/ipv4/ip_default_ttl folder somewhere. Long story short I had to downgrade to an older version of android because after a certain update access to the TTL settings was blocked even with a rooted android phone. I confirmed this by installing Android 14 and used magisk and several other programs inside FDROID to try and change my TTL settings.
It was working flawlessly no data caps on my network as a failover internet. But I decided I wanted to try one more time to update to the latest firmware and see if I could get it to work. Big mistake because now I don't remember what I did to get it to work. It would be nice if graphene OS would allow some way to change this since many people who are concerned about privacy would like to use this method to enhance their privacy since you can buy a prepaid sim and have anonymous internet.
Im not sure if these new changes to the Andoird OS prevent Graphene OS from implementing a feature like this but it would be awesome to say the least since I will have to remove graphene OS and go back to an older version of Android. I think my use case is rare since I dont care about the privacy of my phone because it is essentially being used as a hotspot and cannot access my network since it is acting as a secondary wan.
I can easily bypass the TTL on my windows computer but like others have said in this thread it is not as easy or practical to change TTL on every client device.