How to change the MAIN Default fonts?

I tried to change the MAIN default fonts to Arial but it doesn’t work and something is wrong now (I have the Arial fonts already installed and working).

To change the secondary default fonts, we do this:
Options->LibreOffice Writer->Basic Fonts (Western)
Then we change the fonts from the drop-down menu. However, if you click on “Default” at the bottom right, it will revert to the MAIN default (Liberation Serif").
So I went to Advanced->Open Expert Configuration->org.openoffice.Office,Writer
then changed all the following to Arial
Default Font Standard
Default Font Heading
Default Font Caption
Default Font Index
Default Font List
I closed Open Office, Re-opened it and the MAIN default is still Liberation Serif!
So I went back to the advanced settings and now everything I changed is set to “void” and I can’t edit those anymore.
What’s going on?

Version: 7.3.7.2 / LibreOffice Community
Build ID: 30(Build:2)
CPU threads: 1; OS: Linux 6.8; UI render: default; VCL: gtk3
Locale: en-US (en_US.UTF-8); UI: en-US
Ubuntu package version: 1:7.3.7-0ubuntu0.22.04.8
Calc: threaded

That is to change the default font.Just set the font(s) and OK. That is it. Done!
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If you click on Default at the bottom it will reset that pane to the factory defaults, overriding what you have just set.
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If you cannot change Advanced back to what it was you might have reset the user profile

I don’t know how to explain… The advanced panel allows us to change those “factory default” bit if we do, we now get void. Strange thing is that Liberation Serif is enabled when it shouldn’t since we have “void”. I even clicked on “reset” and nothing changed.

The Advanced settings used to have a big warning that it was all at your own risk.
It is just the same as changing registry settings directly, you can cause LibreOffice to no longer work.
Probably you just need to reset all your configuration changes back to factory by Help > Restart in safe mode and under Reset to Factory Settings select Reset settings and user interface modifications.
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If it were me I would rename the user folder, allow LibreOffice to create a new user folder and copy the old user sub-folders back over the new ones, see LibreOffice user profile - The Document Foundation Wiki

I already did that and same thing…
I did: Help->Restart in Safe Mode
Then: Reset to Factory Settings->Reset entire user profile-> aply changes then restart
Next, I went again to: Tools->Options->Advanced->Open Expert Configuration
And to: org.openoffice.Office.Writer->DefaultFont and everything is till set to VOID
Same with DefaultFontCJK and DefaultFontCTL

At this stage I would consider reinstalling LibreOffice

Try first going to Tools > Options > LibreOffice Writer > Basic Fonts (Western) and setting the fonts you want, then press OK.

I just went ahead and renamed user by user-old then launched Wruter again. It created a new “user” folder then guess what? same thing! nothing changed.

I may have discovered a weir bug…

The issue is not with changing that setting.