according to sammobile.com your phone model is SM-G9910....is this correct?

and if so it looks like that is the most up to date firmware for your phone....according to sammobile which is a legit place to go for any firmware updates needed.

 

You do not have the international Exynos model, G991B.

Yours is the G9910 Snapdragon regional model for China, Hong Kong and Taiwan which are still on Android 11. See...

https://www.sammobile.com/samsung/galaxy-s21/firmware/#SM-G9910

 

That's actually the Hong Kong(SAR), Qualcomm Snapdragon variant of the S21 you've got there. although it will work internationally no problems. I believe Samsung haven't rolled out Android 12 for the China S21 Snapdragon variants yet, including HK and Macao. And if you bought it in the US and not HK, then it was a grey import there.

Also FYI Samsung Belgium many not be able to deal with warranty claims for any issues on Snapdragon devices that were intended to be sold in China, etc. The EU countries get the S21 Exynos variants.