How do I less a filename rather than an inode number?

Use less --follow-name if your version of less supports it. That option was introduced in version 416.

The less option --follow-name is only part of the solution;
To replace tail -F, another argument is needed:

less --follow-name +F file.log

The option alone like less --follow-name file.log does not actually start following the file updates. You need to enter the follow mode be pressing ShiftF.
(Exit the mode to navigate by ControlC.)

Instead of following the file, --follow-name modifies the behaviour of less.
It makes the command key ShiftF inside of less follow based on the file name, not the file descriptor.

Also, there is no normal option to start less in follow mode.
But you can use the command line to give keystrokes to execute after startup, by prefixing them with +.
Combining the modifier option with +F, less will actually start in the (modified) follow mode.

Use +F alone for the equivalent of plain tail -f:

less +F file.log