Singapore DTT: channels is scheduled to have some upgrade on its audio track:
Result:

As the viewers may experience very minor disruption as such, will still be informed on social media and presumable elsewhere too.
-------Malaysia DTT: All RTM channels upgrades to HD on earlier April, hence all channels migrates into another frequency, which is Mux 2.
Result:
Error 404. Content not found, because nothing happen.
MYTV myFreeview did not inform to the viewers that viewers are required to perform auto scan (or manual scan) on their TV sets or DVB-T2 box, especially those who didn't use MYTV branded DVB-T2 box.
Until the public turn chaos, customer service hotline and Facebook page are flooded with queries, wondering why all RTM channels becomes "No Signal" out of the blue, then only they advise viewer to perform auto scan
few days later on its Facebook page.
This is just like:
Viewers:
MYTV myFreeview:
In conclusion, when there's such issue like this, they expect customer to call them and ask first, then only advise them what to do.
Inform the public on social media? No hurry la... Do it few days later also nvm.