Ubuntu uses MKV to release subtitles

Mkvextract
The program "Mkvextract" has not been installed. You can use the following command to install:
sudo apt install Mkvtoolnix
Mkvextract:command not found

Ai Mkvtoolnix
....
Mkvinfo!$
Mkvinfo 560--\[hysub\]\[conan\]\[560\]\[1280x720\]\[x264_aac\].mkv
+ ebml Head
|+ Document Type: Matroska
|+ Document Type version: 2
|+ Document Type Read version: 2
+ clips, size 242491148
|+ Locator Header (subkeys will be skipped)
|+ ebml Voids (size: 4027)
|+ Clip Information
| + timecode Scale: 1000000
| + Mixed Flow program: libebml v0.7.7 + Libmatroska v0.8.1
| + Writer: mkvmerge v2.9.8 (' C ' est le bon ') built on modified 13 2009 12:49:06
| + Duration: 1494.762s (00:24:54.762)
| + Date: Tue Dec 04:29:15 2009 UTC
| + clips uid:0xb5 0x68 0x73 0xca 0xa0 0xce 0x80 0x98 0xbb 0x6b 0x0f 0x9c 0x35 0x16 0x1f 0x51
|+ Clip Tracks
| + One track
.....

| + One track
| + Track No.: 2
| + Track uid:757608576
| + Track Type: Audio
.....

| + One track
| + Track No.: 3
| + Track uid:2825463219
| + Track Type: subtitles
| + Enabled: 1
.....

Mkvextract Tracks!$ 3:560.ass
Mkvextract Tracks 560--\[hysub\]\[conan\]\[560\]\[1280x720\]\[x264_aac\].mkv 3:560.ass
Extracting track 3 (http://www.aliyun.com/zixun/aggregation/29788.html ">codecid as ' A_AAC ') to file ' 560.ass '. Container format: Raw AAC file with ADTS headers
Progress: 27%

Actually, the new one has mkvtools.

After installation, as with win usage, the man below is OK

can be individually extracted subtitles, video streaming, sound track

You can also edit the header of the file again

Code:
sudo apt install Mkvtoolnix Mkvtoolnix-gui

It is really a good tool to extract, merge subtitle files into video files, turn off or open unwanted tracks, and merge video files!

It's great! It's worth recommending!