In Sweden we have something called "Bank-ID" its a digital ID. Most services such as logging in to renew medical receipts, access your tax information, and file your taxes, pay your bills, access your bank. Buy insurance, cancel insurance. Think anytime it would be unreasonable to not verify your identity, you need bank-id. It is basically a certificate you generate together with your bank, that can only be accessed through the bank-id app/application depending on if you have it installed on your desktop or phone. Everytime a website has Bank-id integrated as a login method. You will need to scan a QR-code with the app or initiate the app from the website. Then type in your code to authenticate. Voila you have verified yourself. This requires their proprietary application, and the certification that lives in the app is issued by Bank-id. So you are locked in

Edit: basically in Sweden any linux phone without working bank-ID would be dead in the water from the start.