Which bands you are looking for?
The S20 Snapdragon variants from Asia have certain limitations in the modem firmware, which cannot be modified (at the moment).
For example, there are no carrier aggregation with LTE on B20, its only supported as single carrier. Look at the attached combos when used within the German Telekom network. In this case the network requested even B32, but not supported.
Also 5G ENDC NSA is limited to anchor band B8 with N1 only. It does support aggregation of B3 and B7 as well, but B8 must always exist as anchor band.
The following 5G bands are supported from the firmware: N1, N41, N78, N79 (there was N3 support before August Patchlevel)
4G bands implemented are: B1 - B5, B7 - 8, B12 - 13, B18 - B20, B25 - 26, B28, B34, B38 - B41 (there are hints that B66 is supported, but not confirmed)
No other bands can be used (at the moment).
My carrier, Orange, is the only carrier in Romania that fully supports my phone, such that I get 4G Carrier Aggregation, Volte and Vowifi (On other carriers like Vodafone I cannot get 4G CA to work) and 5G at the moment is also fully supported, as the only band used at the moment is N78. Starting next year, they will add N1 and N76 I think (will edit the post with the exact bands once I find exactly which are going to be implemented). That's why I asked, because starting next year I will not be able to get 5G CA with the supported bands of my phone. A friendbofine suggested that I use QPST, but I couldn't get the software to detect my phone, but I don't think I would have known how to "add" the bands anyway.
edit: these are the bands that will be added across all carriers starting next year: n12 / n14 / n83 / n20 / n75 / n76 and n7.