MTU or other issue

Problem: When routing SIM (cellular) data through Ethernet Tethering from an Android phone to a PC, GTA Online and FiveM fail to connect to game servers — connection to server times out / fails to establish, even though general internet browsing works fine. Working configurations (no issue): Phone connected to a second phone's WiFi hotspot → Ethernet Tethering to PC → GTA/FiveM works SIM data via USB Tethering → GTA/FiveM works SIM data via phone's own WiFi Hotspot (to PC's WiFi) → GTA/FiveM works Failing configuration: SIM (cellular) data → Ethernet Tethering → GTA/FiveM fails to connect to server (browsing/TCP traffic works fine, only game UDP traffic seems affected)