Can a flashed ATT Lumia 920 operate in Europe?

[Windows Central Question]

I flashed an ATT Lumia 920 RM-820 to RM-821 to use it in Europe (mainly France). I can't use LTE with my operator although this Lumia is supposed to be compliant. Operator name is "Free Mobile" and runs on the 2600 Mhz band.

Does flashing allow the change in LTE frequencies from North America to Europe (i.e. just a software change), or is it a hardware issue?

Current specs of my Lumia:
- Manufacture name: RM-821_eu_france_267
- Mobile Operator: 000-FR
- Configuration ID: 473628
- Core Build ID: 3051.50009.1451.10458

 

[RumoredNow]

Hardware. The SoC will be physically "tuned" to certain bands and software will not change this.