You don't say what device you're using or what OS, but if it's a Mac, then you can use the menu View>Sort

to sort by title.
The filename is not the title, although it is true that in the absence of a title thumbnails will show the filename--

but that is less bright, so you can tell the difference.
Filenames are pretty much ignored by Photos. Filenames are important in File Management systems, but they really don't have much to do with a picture in an Image Management system. Not all pictures in Photos are files, so filename has less meaning. For instance, when you edit or crop a picture, that image is not a file, but rather it is information combined in a database. When you save that as a file you are creating a brand new file, so it can have whatever name you like.
If you're sure that the filenames are what you want to use, then you can run a script that adds the filename to the Title. There are some scripts here:
Thematic Index to Photos for Mac related User Tips
You can search for Filename.
I use the app Photos Workbench ($30) that, for me, is way easier to use. You get a vast array of things that can be put in the Title field, like this:

I use a standard form for the Title that includes date, counter, and description:

By changing the counter I can arrange pictures in a different order. When you export a picture in Photos, you can have the new filename be the Title, so slideshows, for instance, show the picture in the order you choose. Titles are part of an exported picture's metadata, so the Title travels along with the picture.
iOS and iPadOS don't show Titles, so I copy title information into the picture's Caption field, and I can add more specific information there.