[Samsung Galaxy S10+ Questions & Answers] beatbreakee:
i would have to claim that AFAIK , tripping knox would only void any warranties directly related to software issues. (ie Android updates creating boot loops, or in that area). While i cannot say the rules are still 100% the same today, I myself had purchased a Galaxy S10, DIRECTLY from Samsung to be used on Sprint, just over a year ago, and then had one of the members on here do the whole Unlock token things for me, then proceeded to flash TWRP and then Magisk. Well not only does Twrp trip knox, but the bootloader unlock leaves that big "Unofficial Firmware" splash screen on every boot. Well about 2 months before the warranty expired, the vibration motor inside the phone failed, and i didnt wanna pay insurance deductible for something that i thought should be warranty related... I did some research and located some articles (you gotta google, cuz the exact sites i dont remember) that said in the EU, consumers won some lawsuits that banned the manufacturers, namely Samsung and LG, from invalidating warranties for consumers who only modified the firmware in their devices. This was targeted at people who rooted their devices through whatever methods. And the result was that the manufacturers COULD ONLY ENFORCE THAT RULE IF THE WARRANTY CLAIM WAS A DIRECT RESULT OF MODIFIED FIRMWARE/SOFTWARE. If the defect was indeed hardware related, and could not be something triggered by the modification, then the manufacturer was required to comply by the terms of the hardware warranty terms that they had provided by sale of that device.

So i took a shot and contacted Samsung Support via the website and chat interface, and requested a warranty repair. Gave the IMEI and SN of my phone, and they said "Yes warranty is available, can you provide proof of purchase" ... i did all that, and near the end i specifically asked the support person "My phone is Bootloader unlocked via Samsung unlock token, so my phone says "Unofficial Firmware" when it starts up, so is that gonna be a problem because i wont bother sending it if so." and the tech took a few min and said, "as long as the phone itself hasnt been modified or the technicians determine that you opened up the device and did any physical modifications, then NO it wont affect your claim. But please note that we (SAMSUNG) do not provide or sell Bootloader unlocked devices or solutions in the US, so if your device is replaced, it will be with a LOCKED device instead!" I agreed, packed up the phone and sent it with the label they emailed me, and about 9 days later i got a package from Samsung with a new looking s10 inside, a charging cord, adapter and headphones. And sure enough it was locked, but i paid nothing, so they definitely honored the warranty. Hope that helps.

(the reason i say i dont know if its still true today, is that i heard through rumor that the manufacturers were in the process of changing the terms in their warranty, in a way that would legally give them the right to block warranty claims if ANY hardware or software was altered in any way! That seems unlikely cuz its exactly the terms they lost the prior lawsuit under, but **** changes when greedy companies get togeter!)