Hello,
RUTX50 cannot aggregate LTE B8 (900MHz) with LTE B20 (800MHz), however, it can aggregate LTE B20 (800MHz) + NR n28 (700MHz).
However, you should also keep in mind, that not all carriers use LTE B20 as an anchor band, so make sure your carrier supports this.
I cannot post a full CA table here, as it simply would not fit, but if you have any further questions, let me know!
Best regards,
DaumantasG