I don't think we need to keep this private, it's worth sharing with those who have the same issue.
I will however attach the source files privately.
I have a file called subs-in.mp4 which has a subtitle track in it.
Here's how it looks in VLC
In WMP Legacy, I can't see any subs, even when switched on
in WMP 2022, I can't see any subs either
So that is the first problem. Subs don't work in WMP.
I then created a sidecar SRT subtitles file, with the same name as a video that does NOT have subtitles embedded as the stream.
subs-ext.mp4 and subs-ext.srt
This also works in VLC the same.
in WMP legacy, doesn't work, the same...
in WMP 2022, I can select the file (this is annoying as you'd have to send all subtitle files with videos when sharing...)
When I select the file, the subtitles are included. But, they are white... so see what they look like below...
Compare this to the original VLC screenshot, where you can read all the text.
So, they don't work, and then problem 2) with the sidecar file, you can't read them...
I had believe that tools like this now had a requirement to be accessible, yet I just can't use subtitles with WMP, and that will be the default app for many people I send a video to...
This really has to work - it's absurd that it doesn't in 2024...