If your device is a foreign version, you might face some difficulties receiving an update.
Every version of realme devices is specialized for a specific region, and the region's version differs in Languages, Network supported frequency bands, and Built-in Apps which will bring different OTA updates. We recommend you to use the device within the same country to enjoy the warranty and update service as it's applicable in the country you've purchased the device.
If the update is available, you will receive a notification message through OTA to be able to update it easily.
If you can't receive an update, you can try to use the VPN to connect to the network of the area where your phone was released to try.
realme UI 7.0: Settings > Mobile network > More settings > VPN > Tap the + in the upper right corner.
realme UI 6.0 & 5.0 & 4.0 & 3.0 & 2.0: Settings > Connections & sharing > VPN > Tap the + in the upper right corner.
realme UI 1.0: Settings > Other wireless connections > VPN > Tap the + in the upper right corner.
realme UI R & Go & T & S & U Edition: Settings > Network & internet > VPN > Tap the + in the upper right corner.