converted lff font files do not work.

The ttf(DejavuSans) file was converted to lff font using ttf2lff.
I looks well made, I can't no error or warning message.
When entering text in the librecad program, I can see the font name created in the font list.
However, even if I select that font, it does not apply.
Any files other than existing fonts do not work

I have tried to reproduce your problem, but I didn't even succeed in building the DejavuSans.lff.
I got the error "FT_New_Face: unknown error". Some years ago I managed to get a result, don't know what I am doing wrong this time.
Can you provide your DejavuSans.lff here for to test if it works for me? Does it have a resonable file size or might it be empty?
 

I have no error or waring message.
but file is size bigger than ttf.
it tested on archlinux.
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[wonhae@office1:~]$ ttf2lff DejaVuSans.ttf DejaVuSans.lff
TTF file: DejaVuSans.ttf
LFF file: DejaVuSans.lff
Family:    DejaVu Sans
Height:    2384
Ascender:  1901
Descender: -483
Factor:    0.00602813
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ttf link
https://drive.google.com/file/d/1bBgAQX7jTXWVQMn2aFbFbK9C3WcXUOXA/view?usp=sharing

lff link
https://drive.google.com/file/d/1HcFDLVtTKHA7Kw3XY-oqa0dHprTTTL0e/view?usp=sharing

It didn't work for me either. It showed up in the fonts list, I could insert the text, but it was the same as ISO.
The same here: https://forum.librecad.org/EXO-font-tp5718649p5718650.html

So there really seems to be an issue with ttf2lff.