Warranty claim also after rooting and flashing of devices
The EU regulation 1999/44/CE stipulates that the warranty remains valid even in case of root or flashing. Only if it can be proven that the defect was caused by rooting or flashing - which according to Carlo Piana and Matija Šuklje is only given in exceptional cases - the manufacturer can refuse the warranty.
EDIT / UPDATE
I haven’t heard anything about that.
Edit / Update
Let’s try unlock OEM bootloader later this Saturday.
Until then you could download this stockROM Android 10 as a precaution: G965FXXU8DTC5
The file is at least 4.5 GB in size.
If you aren’t a Premium Member of Sammobile, the download as a Non-Premium Member takes 18-24 hours at approx. 15 kB/sec.
In about six hours (slow speed) you can download it for free here.