Recent update:
I also checked:
v3.0.6 (x32 on Win7x64 Pro) - no autoloading, only manual
v3.0.7-20190124-0510-win64 (nightly) - no autoloading, only manual
v4.0.0-20190124-0831-dev-win64 (nightly) - no autoloading, only manual
v2.2.8 (x64) - autoloading works ok, installed this one and I'll try it
I just found:
https://trac.videolan.org/vlc/ticket/21462
It seems that VLC since v3.x is not supporting the autoloading of subs in TMPlayer or similar format with .txt extension, and will not support them anymore.
Proposed solution is: "use different subtitle format". Not the best solution IMO - I manually and thoroughly edited many of the subtitles before burning them on DVDs...
Just tried this:
https://addons.videolan.org/p/1276669/ - it needs additional speps to properly install and even then - it needs additional clicking to activate the subs.
So it does not make the solution easier, and therefore v.3.x will be not all-in-one best player for me and I suppose also for many people who have movies burned on DVD-/+Rs.
Like user sc0ty said: "adding the option to edit list of extensions of subtitle files would be the best option"
Else if the next step will be in similar flavour like: "oh, there are some problems with some format, so then VLC will drop earlier mostly proper behaviour or simply VLC will drop the support for that format" then I will be simply forced to switch to other player.