[moviespectator]

You're probably using Wireless networking, which will not work.
You need a fully wired network to have "cast to device" working smoothly.

Nope, it's Gigabit Ethernet with stable wired connection.

[Shark007]

my personal experience is from Windows 8.1 where Directshow could be used for DLNA playback.
Once that support was dropped, I havent used any DLNA playback.
I am not in a position to school you on using the modern Apps.

[moviespectator]

Thank you for trying! That "Media Play" app is not what suits my needs. It casts media to my TV but won't let me direct the library from my TV remote. 
Windows Media Player pretty much does, but lacks to show MKV HEVC files over streaming. 
My research shows there are problems with HEVC MKVs with other MS products as well and a dying WMP is not going to support it soon. Since it's called "Legacy" lately.  
It's kinda bad to have the need to install a different media server software like Plex or so, to be able to show (hopefully) all files there are, when that functionality is already built in Windows.

[Shark007]

I do wish you luck.

[moviespectator]

Thank you and to you as well! 
And thanks alot for your effort of putting out your codecs and WMP improvements that come with by that! 
I was researching and trying that streaming over network last year and tried Plex at first, but its DLNA functionality is limited. 
Then I tried that Windows built-in streaming offering and came across your codec pack last year. Your thumbnail generation works in DLNA too! It's only that HEVC MKV files are not showing and subtitles (included and external) are not showing. 
Perhaps I should get an external hard drive and plug it into the TV directly

[Shark007]

Just to inform, subtitles have NEVER worked over DLNA.
It is possible that if you were to use mkvtoolnix to remove the subtitles from the MKV's, the HEVC files may begin to show up.

[moviespectator]

Thank you even for that! That's good to know. Subtitles are shown as available, but if chosen they don't display.
I know mkvtoolnix well, but I guess I'd need to look for another solution than DLNA now, would like to keep the files together as they are.