This is a feature of Optifine which I made great use of, and while most optifine features have a fabric mod replacement, I haven't been able to find one that simply adds antialiasing, and no AA makes playing the game at lower resolutions a rather rough experience.

It looks like this issue has not had any active discussion for a long time but to expand on @Ictoan42's statement, I still do not know of any good Optifine alternatives for anti-aliasing, and having it supported natively in Sodium would be amazing. The current solutions of using mods to render the game at higher resolutions and then downscale them with linear filters and also using the Nvidia Control Panel to force anti-aliasing or using Dynamic Super Resolution to downscale the frame buffer from a higher resolution usually has drawbacks such as strangely affecting mouse input handling or adding transparent lines around block edges.