Uncompromisingly insist on only using things you have ultimate ownership and control over, even when that means dramatic and life-altering inconvenience, and where those things don't exist, build them yourself.
Unfortunately, "build it yourself" is relatively easy when it comes to software, and almost impossible when it comes to the hardware running that software. It doesn't matter if you have full ownership of a complete open-source stack if no hardware manufacturer will permit you to run unsigned arbitrary code. The lack of open hardware--chips that you could build in your garage using materials nobody could reasonably prevent you from acquiring--is the lynchpin upon which open source software will wither and die.
There is already plenty of open hardware, it's just not this-year's-top-performance.
In the category of ~1-3 years' performance lag you get Rockchip and friends, which are closed hardware that allows open computation. See computers made by the company MNT as an example.
In the category of ~5 years' performance lag you get "soft" cores, where you buy an FPGA (dynamically reprogrammable hardware) and make it run a CPU you design yourself. If you want to, for example, make your CPU have more cache and fewer ALUs, you can do that by tweaking some files and reprogramming the FPGA. This has a cost in terms of power efficiency and runtime speed, but you can absolutely run a full Linux desktop experience on an FPGA today, and the hardware has no way to try to prevent you from running any software.
You can solve the problem of all the cellular basebands being closed source with either software-defined-radio or using a closed USB/PCIe cellular modem connected to an open processor.
Despite my hopes, I somewhat doubt that anyone would accept computing on the sort of chips that one could produce in their garage for less than $10,000 capital investment. You can, probably, with some effort and research, produce something analogous to the original Intel chips from the 70s in your garage using off-the-shelf tools. Sam Zeloof has blazed the trail here: https://www.youtube.com/watch?v=IS5ycm7VfXg . And for a less than a million it's not inconceivable that a municipality could produce chips that would be at home in the 90s. Maybe that would be enough for a lot of tasks, especially if you're willing to resort to hardware coprocessors for common tasks like media decoding and encryption, but it would take a huge sea change to get people to accept it, and nearly all of our software would need to be rewritten.
Unfortunately, "build it yourself" is relatively easy when it comes to software, and almost impossible when it comes to the hardware running that software. It doesn't matter if you have full ownership of a complete open-source stack if no hardware manufacturer will permit you to run unsigned arbitrary code. The lack of open hardware--chips that you could build in your garage using materials nobody could reasonably prevent you from acquiring--is the lynchpin upon which open source software will wither and die.