FF won't install as a filter in Photoshop 25

Forum user CFandM has produced a video that explains how to manually install the FF plugin. The video is about a different version, but it should work by using the proper version directories (in your case FF12 and PS25.1):
https://www.youtube.com/watch?v=HiO8b_rHBWs

I have a similar problem, but not quite the same:

I just updated to Photoshop 25.3.1
After which, I ran the FF 13 installation program, but the option for installing FF as a Photoshop Plugin was not displayed.

I previously modified FF 12 according to instructions on these forums, so that I could keep using it as a Photoshop plugin after a recent Photoshop update disabled it.

Photoshop is still showing FF 12.007 as the current plugin (working correctly), and I can't edit the FF program plugin config file because when I tried saving the edit, I got a Windows error saying access denied, even though I was running as Administrator. There may be other things that need to be edited, but I'm not sure.

Never had this problem before.

Can someone please help me?

I have tried all this, but Filter Forge 13 will still not "show up for work" in Photoshop 2024 Beta.
Any ideas or help will be much appreciated
And please spell it out in details since I am not a professional and need it explanationed to me as if I was ten instead of sixty seven

Yes, that is what I mean by writing "I have tried all this" - I have both watched the video and done what it says. And changed "false" into "true" in all the places I could find it. And in general follow every advice already given here. I hoped, when writing the post yesterday, that somebody had something extra/new, but that might not be the case, I guess

I can use FF 13 as a standalone, but it won't show up in the list of filters in Adobe Photoshop (Beta) even though it promised to install itself there automatically when I downloaded it ... So I don't know what to do more.

Glad you got it working. I did just download the PS beta and tried it myself and the above video is still relevant. PS has changed but the folder structure for PS has not changed for many versions.