[kevwag]

They are probably using different subtitle format for TV channels. Here in Finland d+ TV channels have subtitles burned in video so I can't reproduce problem.

Can you make bug report to https://github.com/xbmc/inputstream.adaptive

Surely the point of d+ moving everything to the .com domain is that everything is on the same platform and works the same way?
From discovery's point-of-view, the service is always accessed by their own proprietary apps or websites so it wouldn't make sense for them to use different formats for different countries - that would mean either having to publish multiple, significantly different apps rather than just configuring one app for whatever region it detects (eg, disable live channels in USA etc) or publishing a bloated app, much larger than it needs to be, just to service these different formats.

Update: I just re-read your post and realized that what you probably mean is that because most of D+ content is originally produced in English, D+have hard-burned Finnish subtitles onto the videos for your region so you don't have to manually enable subtitles.
Are there any shows you can think of that are originally produced in Finnish? My guess would be that those shows would not have the hard-burned subtitles and probably have the normal optional type. 

I don't mind posting a bug report if you're 100% sure that InputStream Adaptive is the root cause of the problem, but if that was the case, wouldn't that affect ALL IPTV channels and also the D+ on-demand content too? The D+ on-demand streams are definitely using InputStream Adaptive as I recently had to change the settings in IS-A to manually select the stream quality (as per my previous post about the new version defaulting to 240p) and the on-demand subtitles are fine.

[-Dis]

Most finnish tv channels use burned in subtitles and if you want finnish subs for finnish show those are mostly accessed from teletext. And because of that d+ tv channels use same method.

For some reason d+ uses many different subtitle formats and for example in USA subtitles doesn't work if you have DRM enabled because InputStream Adaptive doesn't support subtitle format they are using.

Although platform is same for all countries (except India) how subtitles are handled in different countries is not necessarily the same. And can depend on what show you're watching.

To be clear all video playback related (also subtitles) are handled by InputStream Adaptive. Add-on has nothing to do with it.

[kevwag]

Most finnish tv channels use burned in subtitles and if you want finnish subs for finnish show those are mostly accessed from teletext. And because of that d+ tv channels use same method.

For some reason d+ uses many different subtitle formats and for example in USA subtitles doesn't work if you have DRM enabled because InputStream Adaptive doesn't support subtitle format they are using.

Although platform is same for all countries (except India) how subtitles are handled in different countries is not necessarily the same. And can depend on what show you're watching.

To be clear all video playback related (also subtitles) are handled by InputStream Adaptive. Add-on has nothing to do with it.

Ah, ok. I'll post that bug report then. I guess I'll have to get them a log file (after deleting all the references to addons that they frown upon lol).
The DRM thing is the same here in UK - can't use DRM with subtitles. I'm guessing that maybe Widevine doesn't unpack and decrypt the subtitles from the stream, so Inputstream Adaptive has nowhere to get them from (if that's the case then subtitles won't work with DRM anywhere).

D+ have a bit of a habit of not correctly tagging their video files and maintaining metadata. Every now and then I get a live tv channel showing a static message saying "We're sorry, for legal reasons, we are not licenced to show this content in your region" which would make no sense - broadcasting protected content, not UK licenced, on a UK specific channel. Widevine is obviously refusing to decrypt the stream because it doesn't meet a certain criterion.

I've also noticed that with a lot of on-demand streams, the audio stream is tagged as "Spa" for Spanish, when the audio is actually English. Plus, two of the live channel names had the "S" missing from "Dicovery" for more than a year. It's all a bit back-yard amateur - sloppy mistakes.

If their technical departments knew what they were doing, they could just have one version of every show with multiple language stream selection like on Netflix rather than hosting multiple copies of the same show. It would be a lot more efficient AND manageable! I guess that's probably beyond them if they can't even tag one stream with the correct language tag.