Many didn't even realize it. Since the new Buddy Board with the new 3D printers from Prusa has been available, it has not been possible to flash these boards with custom firmware without losing the warranty.
This affected the Prusa MK3.5, MK3.9, MK4 and the Prusa XL. Fortunately, Prusa has changed its mind and now the broken seal no longer voids the warranty. Thank you Prusa <3
You can find out more about breaking the seal and flashing custom firmware here: https://help.prusa3d.com/article/flashing-custom-firmware-core-one-mk4-s-mk3-9-s-mk3-5-s_814967
Now third-party providers can once again offer custom firmware with their upgrade products. Especially my Prusa MK3.5 with Bondtech LGX upgrade would be very happy about a customized firmware. However, it is unclear whether Bondtech will offer this at all.
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