In Linux, when creating a new ReaScript, clicking "NewScript..." button in Actions window opens the save dialog. But the extension selector does not force the real extension of the file. And so when no extension (.lua) is manually typed-in, then the file always gets "*.eel" extension.
It took me long to find out why the LUA code I am trying to paste in ReaIDE is full of errors until I accidentally looked at the scrip extension in titlebar which in fact was .EEL
In Windows it works as expected, if you select the extension from selector, it gets added to the filename edit line (and also filters the directory view).
In Linux it only does filter the filetype of the directory view.
(REAPER v6.35rc5 Linux x64, Linux Lite 4.0 x64)