MikroTik

I have an RB4011iGS+5HacQ2HnD-IN (RouterOS 7.11.2) router with pci-express wifi card (R11e-2HnD?)
Can i change this pci-x card to Wi-Fi 6E AX210HMW (Mini PCI-E Wi-Fi 6 AX200 802.11AX)? or RouterOS does not suport pci-x cards from other manufacturers?

RouterOS does not suport pci-x cards from other manufacturers.

It is not that clear cut. When you have a card from another manufacturer with a chipset that is also used in other MikroTik devices, it can just work.
In fact I have suggested that this may be a solution to have both 2 GHz and 5 GHz WiFi with wifiwave2 on the 4011.