Fn buttons doesn't work at Precision 5550 with Ubuntu 20.04

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Does anyone, from community has any suggestion?

My current conclusion, that Dell laptops, doesn't not work properly in Linux.

I've tried to use the harddisk from Dell Precision into an old Lenovo Thinkpad (L series).

And everything started to work fine, Fn keys. Even the Dell docking station (WD-19) worked much better with old Lenovo, than with Dell.