There are always exceptions, but you should feel confident when you choose SSL because it covers over 99% of internet users.
SSL is supported by the following popular browsers (among others): Chrome, Firefox, Microsoft Edge, Internet Explorer v5.01 and above, Safari, Opera v7 and above, Brave, Samsung Internet, and Sony PlayStation.
The complete list is too exhaustive to include here, but unless someone is still using their Windows 3.1 machine to go online, their browser probably supports SSL.