Trials of Mana only supports four common 16:9 display resolutions.
What about the other 16:9 displays, the “golden ratio” 16:10s, and the ultrawides, then?

I stumbled upon the file in my Documents folder (the one OneDrive backs up because it’s never heard of Steam Cloud), which conveniently contains my game preferences in plain text, plus a handful of “secret configs”.
Inconveniently, however, changing the file does nothing, and it’s not just the display resolution that’s not applied.
Instead, this is apparently only some sort of readable cache that the game overwrites each boot.

The settings are actually in next to the game saves, also “conventionally” in the Documents folder.
But I found no 1920×1080 in the binary file, only a mention of “HD”.

So, that is why Reddit tells people to edit the .exe —
The four resolutions are the only four hard-coded enum options of `ESelectResType`.
For example, the choice ::RES_TYPE_HD is hardcoded to correspond to the resolution 1280×720.

To conclude, for many displays, the only way to match the game with their resolutions is to hack the game, never mind the EULA.
By the way, if you want to check out the files yourself, you don’t need a hex editor because you can find the enums in their text form.

End of the miniblog –?

Well, I didn’t only mention 16:9 in the first paragraph, did I?
My previous computer had a 16:9 display, but my new computer has a 16:10.
I booted the game up on my new computer, and …😖!
Everybody and everything became skinnier as the 16:9 game forcefully stretched itself to fill my 16:10 screen.

Some people prefer it this way over the black bars, but I don’t mind the edges and would rather have the game in its correct proportions, like what most other games do.
But, if even the simple numbers of resolutions are limited to hardcoded pick-ones, chances are that so is the behaviour to stretch rather than to letterbox for 16:10 or pillarbox for ultrawide.
Whelp, Windowed for us it is.