The phrase "opt into" implies there's a choice, but the rest of that paragraph implies there isn't.
As far as I can tell there is no option to "buy out" an e model to remove the subscription requirement. Given HP's history I suspect once this annoys the wrong person it'll turn out to be pretty trivial to break, but for now if you feel the need to purchase a new HP product you should definitely avoid the ones with an e in the model number.
AFAIK Brother hasn't tried anything like this (yet?) and they're cheap so if they fit your needs I recommend them.
Then I bought a far cheaper second-hand Brother printer, turned off firmware updates, and have continued using 3rd party toner. So only kind-of fuck them, I guess, because their printers do the job pretty well.
But I am glad I switched to mono, because the colour MFC would have cost AUD$550+ on genuine toner (3 colour + 1 black). Too much for casual usage once a month.
Damn, that sucks, I'm happily using my old Brother printer and was thinking about second one. Did it not let you override that warning in service mode[1]?
[1] Brother printers have a hidden menu where you can set cartridge values to different ones than read by printer's sensors. Godsend if you are using very cheap 3rd party cartridges, as they sometimes report their capacity as 0%. The way to access it depends by model, for OP's model I found https://www.youtube.com/watch?v=J6lsUBu1TDg
The simpler solution is to just avoid purchasing HP products.
Got a scanner instead that was fully supported on Linux and cursed HP for three generations.