I'm seeing a few comments suggesting OpenWRT, which is what I use and love: the correct response to this level of capitalist tomfoolery should absolutely be to 1. buy hardware that supports FOSS out of the box, or 2. install FOSS firmware.
BUT: OpenWRT isn't for everyone. Installation on supported devices is usually pretty easy, but it does require being invested in setup, maintenance, and understanding of the software. There is little built-in handholding, and most setup beyond basic functions requires reading the docs and wiki; sometimes, some functionality requires running commands directly on the device rather than the LuCI web-interface.
This kind of understanding and investment should be the end-goal of all privacy-oriented tech users. Technology is complicated, and each layer of handholding that devs add also necessarily obfuscates behind-the-scenes functionality, which runs counter to privacy and security. That being said, the barrier for entry to privacy-respecting tech shouldn't be "a masters in CompSci," and thus any alternative to major tech brands is still a step up from just accepting what they give you. Just be aware that your current firmware may be a stepping stone towards software freedom, instead of a stopping point.