NoWayOut What seems to have been established so far is that increasing the TTL value by 1 does not work on Windows and MacOS. It appears to be working on Linux.
Two Linux kernels (Android and another one on a laptop) may well fingerprint the same way. If there is no TTL jitter then the tethering may go unnoticed. Windows, macOS, Plan 9, etc., may fingerprint very differently, in which case TTL tweaking by itself won't work.
Meanwhile, I don't think my carrier has a "tethering quota", though I admit I haven't checked recently. Maybe switching carriers is an option?