Sure thing. Many of the January 6th protesters were tracked and identified by the government through their mobile phones. It seems that Google location services might have been involved in this specific case, but in general any mobile device is a very powerful location tracker on its own.

Any device that connects to a cell tower must broadcast an equipment identity. Modifying a device's International Mobile Equipment Identity (IMEI) is illegal in the USA if done for the purposes of defrauding (no clue what counts as defrauding) and is always illegal in the UK regardless of context.

As I understand it, most mobile devices will broadcast this IMEI even when the device is turned off or it's SIM card removed. Only airplane mode, removing the battery, damaging the device, or moving the device somewhere its signal cannot escape are enough to prevent this signal from reaching cell towers.

Cell companies use this signal in order to shut off service to stolen devices and to triangulate its location. Its location is used to maintain an ongoing connection with the device and is relayed to emergency responders in the case where the device calls emergency services. Cell companies also store this location data for extended periods of time. They turn this information over to the state on legal request, and will sell it to private parties. This information was used extensively by Dinesh D'Souza in the research he did for his film, "2000 Mules."

In order to mitigate this, sensitive individuals such as criminals will often use devices (and by extension, those devices' IMEI's) that cannot be associated with them. These are what people refer to as "burner phones." There are a few simple, but inconvenient rules for burner phones. They must be bought with cash or through another equally anonymous channel. Their mobile subscription must be purchased anonymously. (This means a SIM card with a prepaid subscription.) The device may not connect to cell towers in any location associated with the owner. The device must never be used to contact anyone associated with the owner's identity. And the owner must be willing to freely discard the device. Hence the term "burner."

These rules make such a device inconvenient and impossible for the average person to use as an everyday mobile device. Even criminals and other sensitive individuals will often own a separate personal phone for this exact reason, though the location and owner of this personal phone will have none of the benefits of a burner phone.

From what I have seen, many of the January 6th protesters did not anticipate that they would recieve attention from the state after their actions, and would most likely not have thought to use their burner phone, even if they had had one.

This is a combination of factors that unfortunatly as far as I can see, has no simple and convenient solution. I have put a lot of thought into solutions that aren't as simple and convenient though.