What I was actually hoping for.. and so far turned out disappointed, is a half-decent LTE/4/5G module that can be Arduino compatible.

Just like ESP8266 (and later -32) variant opened up the IoT over WiFi, there is a potential industry-wide opportunity space for a decent, low-cost, always-online (just bring SIM) hobby board. Without awful vendor tooling. And ideally without "modem-to-something" bridge (which almost always means AT+ and vendor tooling..)