Displaying your screen content to others during a Teams meeting or call for collaboration
I'd check the Collaborative annotations setting in the affected users' effective Teams Meeting Policy first. Microsoft lists this as the policy that controls whether participants can collaborate while screen sharing.
Since they already plan to compare the custom policy with Global, that's a good test. You can also check the effective policy with Teams PowerShell and compare it with Global, rather than only comparing the policy templates. Microsoft notes that direct user assignments and group assignments can affect which policy is actually effective.
If Collaborative annotations is enabled and the option is still missing, I'd then test the same user with the Global policy and the latest Teams desktop client. If it works there, that would point more toward policy/configuration than the client itself.