@sheddi @pluralistic I think there'd be quite a market for retrofits of this sort: open hardware appliance controllers running open-source software, to rip and replace the stock controllers. Ask #lawfedi to be sure, but I'm pretty sure it doesn't count as DRM circumvention to remove and discard the DRM-containing electronics and install de novo replacements.
I imagine the retrofit kits could be sold either as boxed kits or pre-assembled, like @frameworkcomputer products.
I imagine there'd also be a significant secondary market for installation services, and perhaps also for retrofit design: reverse engineering non-computerized wiring; scanning and quantitatively modelling appliance cavity geometries; designing compatible adapter circuits between a PLC, programmable microcontroller, or SBC and the operational hardware (e.g., motors, fans, and heaters or compressors).
And I imagine there'd be a need for an (ideally federated) community repository of retrofit spec files: detailed internal physical dimensions of cavities in appliances with their stock controllers removed; wiring diagrams and documentation of residual non-computerized electronics; connector specifications (e.g. which type of wire end to use); instructions like on @iFixit for opening, removing stock controllers, installing replacements, and closing; and #3Dprinting files for controller mounting brackets and the like. This would best be community funded like most of the rest of the #fediverse.
I imagine there'd also be room to community fund development of firmware or software for the replacement controllers.
There could also be a tertiary service market in safety testing and re-certification of retrofit appliances, in case anyone wants to resell their retrofits with insurance and all.
And I second favouring "Unauthorized Bread." Unlike the poor migrants in the book, though, enough of us can currently afford to hack the hardware rather than the firmware, by removing and replacing all but the passive and operational components, discarding and replacing every programmable but not (intentionally) owner-reprogrammable component. Indeed, I'm sure it's best those who can, start working on this immediately, before #GreatDepression2 kicks in.