Hello, I recently noticed that game updates are not showing when I go to my (account -> ) games -> my collection -> updated tabs.

Anyone has an idea about how to fix that?

Several weeks ago I made a support request in regards to this, Request #616533, to which gog has not bothered to answer. Worse, they have not said a word about the issue anywhere I've seen and I asked for that, at least. If they don't do something soon, I'm going to try to organize a strike against giving gog anymore money until they either work this out or give a reasonable explanation for treating customers so poorly.

If you haven't found it already by now, see here, I'd call that the main thread for this. (No fix you can apply, GOG stopped flagging updates.)

Is it a temporary change?

Only God.....I mean Gog knows.. :).

That's infuriating, anybody who has 50+ games on their library and keeps games installers literally needs this feature.

I also noticed the game update icon never shows anymore. It's weird that it hasn't been fixed yet.

To add, it’s part of a wider issue with website downloads:
https://www.gog.com/forum/general/provide_a_full_and_complete_changelogged_download_system

I believe this is another "Just Use Galaxy"™ issue. The library is continuously being deprecated in a "step-by-step" manner.

I invite anyone who is inconvenienced by the lack of an update flag in their library to join me in boycotting gog until they solve this problem.

It's been at least 5 weeks since this lack of update flags started. It's been over 4 weeks since I wrote started a thread concerning this issue. It's been three weeks since I started a support request, "Request #616533" and have had no response. I will not support a company which does not provide adequate support to its customers, such as at least issuing a statement when there is a problem, much less dealing with the problem. gog will receive no more money from me until they take care of this problem. Please join me if this is a problem for you.

So today there was a Terraria update, but once again the GOG Update Icon didn't show up. Will this ever be fixed?

Soon to be replaced with something new to cover that functionality, together with the new GOG mixes.

Yeah, and a new forum as well! ;)
Just kidding! I don't expect any good news from GOG; it seems all hands are on "Galaxy" deck.

No.