As per NPCI there are two types of Aadhar linking
1. Aadhaar Linking at the Bank's CRM/CBS (Central Banking System/Software). This is done at bank level and mostly all accounts have Aadhaar todat.
2. Aadhaar Seeding: This is Linking A/C with Aadhaar at NPCI layer. For this to work, Aadhaar should already be linked at Bank's CBS.
Now 1 is done when you open an account and while opening there is checkbox for Aadhaar seeding too and branch people usually check it even if you somehow miss it. So for almost all banks Aadhaar Linking and Seeding is done as long as you haven't explicitly asked them not to
If you or branch people missed 2 (seeding) somehow (Like I did for PNB) NPCI has provided a portal to seed account without visiting the branch.
Aadhaar UPI only works if Aadhaar Seeding is done. Other services that can be availed after seeding DBT (this is usually done by default when seeding but you can opt out), AePS (sometime back this was opt in but now it's disabled by default)