Open source stuff will be hard to ban, but just like in the financial sector in this post Ukrainian world a lot of nononos has been crossed.but it's still open source. Just look at how linux is still present in russia, sure some providers have stopped services but that's not the same as a ban
The scenario i'm thinking of is that financially eastern big tech like Huawei won't be able to sponsor their board chair anymore. Like the saying goes "If You Are Not at the Table Then You’re Probably on the Menu" western big tech are able to sponsor their board chair so they can influence Linux development to advance western tech or slow down eastern tech etc.
Western big tech might assign pro western top maintainers and code reviewers to get their stuff in first etc in the "official" version of linux. Sure its possible for Huawei to maintain, compile and patch their own version but then you're always one step behind from the western big tech companies that sit at the table. It also cost extra effort and man power that could have gone into creating new features.
If i was in a position of power that's how i would do it if i had to plan it out. It's not a complete exclusion its just relegating Eastern tech companies to the back of the line and out of leadership position. We have seen this sort of behaviour already with Github banning Iranian accounts(because sanctions prevented doing business) or open source packages that do file system/console textual message related stuff only on Russian computers etc.