Told by Netgear that Nighhawk M1 will NEVER get firmware updates if you buoght it unbranded

NiklasK The information you received is incorrect, there are two types of M1 mobile hotspots the ISP branded version and retail version. For UK and EU the MR1100-100EUS is the retail SKU there is also a EE UK branded device. If you have the MR1100-100EUS SKU then the new firmware would be tested and if all tests pass it would be released to the Netgear AirCard update servers. Once the new firmware is uploaded to the Netgear AirCard server you would get a notification that update is available. If there is no notification you can simple get the latest version by logging into your device and going to Settings-->Administration-->Firmware Update and click on Check for Updates button. if  update is available it will be downloaded to your device.

For ISP branded M1 devices the FW has to be approved by the ISP and ISP would then load the  FW onto their update servers and send out a notification to devices that update is available and users would just do the update. 

As far as Netgear support goes they always recommend that ISP is the first point of contact for retail devices because if there is issues with SIM or LTE network they are not able to support it.

Furthermore, if you are having issues that are not related to LTE network or the SIM then I would suggest to get in contact with their support if the issue still continues after updating to latest FW version.