Subject 1: gog should make a store application for the mobile platform to sell good old mobile games (gomg) that are no longer exist / playable on the mobile platform ?

Subject 2: should gog provide a multiplayer service for the good old games that are no longer have their multiplayer works nor all game multiplayer servers being shutdown since long time ?

Subject 3: gog is just a game store, it's not a full gaming platform for your games (galaxy is optional) and this is a good thing. There is nearly zero integration between the gog games and gog itself as platform.
I do believe that gog must have both sides at the same time, the side that shows gog only and only as game store that sells a DRM-free games. And the side that shows gog as a whole giant gaming platform.
The gog galaxy (which is gog attempt to be more than just a game store, a platform) is limited, and It's not enough.
The steam OS which is steam attempt to be more and more like a gaming platform, a place where you can add friend chat with them, having a place for mods, having its own multiplayer network and so on.
And I do believe that gog must have all the following features to be kinda of a full gaming platform:
1. purchase a game, install it and play it automatically no matter what operating system you are using.
2. add friends on gog to play with you, having chat and voice chat functionality,
3. having group and party functionality.
4. having achievements, cloud saves,
5. having a place to instantly download and install (manage) game mods with one click.
6. the ability to manage your games media like take a screenshot nor record video for your games.
7. global scoreboard
8. your playtime and an advanced analytics about your playtime.
9. some tools and built in utility like FPS counter.
10. integrated media player to play the OST's of your favorite games directly from galaxy.
11. goodies manager to surf your favorite game goodies like songs, pics, artworks, and other stuff right from your galaxy client.
12. more other possible features that could contribute to make gog more like a whole platform / operating system designed for games.

Oh boy...

Many old mobile apps stop working because of OS changes and both Android & Apple tend to have far worse backwards compatibility than Windows comparing games of the same age. Eg, running a 2007 game on a 2024 OS = Android 1.0 game on Android 14 or a Windows Vista game on W10-11. The latter has vastly more natural backwards compatibility there. The other reason there's no "GOG for abandoned mobile games" is most mobile stores are filled with disposable "Freemium" crapware stuffed with In-App-Purchase monetization (locking games to accounts, aka DRM) that are naturally incompatible with working offline DRM-Free. When they reach EOL, the devs would rather throw another "identical game but different reskin" knockoff to monetize. See Candy Crush Saga vs Bejewelled, etc. And many of the few decent ones worth buying are often PC games that were ported to Android in the first place (often with more bugs than the PC version) as well as ScummVM games (that don't need mobile specific versions in the first place). Aside from the fact GOG can't afford it, they don't have access to most games source code anyway to change things like hard-coded servers. I stopped reading here because yes it is a good thing that GOG aren't blowing even more money on top of what they've spent on Galaxy, trying to convince the "No Steam, No Buy" crowd to abandon Steam. Epic are struggling with that even with "Fortnite money". Galaxy still hasn't paid for itself. Spending 10x more money on top stuffing offline installers with a GOG-branded Discord knockoff, custom GOG benchmarking suite, GOG branded media player, "even more analytics / telemetry", etc, is very definitely not why many of are here.

Half the stuff you're asking for, eg, "taking screenshots, playing music and an FPS counter" hardly need a client. You have a keyboard with "Media Keys" (Play/Pause, Vol Up/Down, Back/Forward) = you've been able to play custom music on whatever media player you use, skip / pause tracks with the game in the foreground without ALT-TABbing, etc, even with client-less offline installers all along. Windows 10/11 Game Bar does screenshots & captures though most people I know use MSI Afterburner anyway for better GPU fan control / overclocking / undervolting / benchmarking / screenshots, etc. And before that, FRAPS. You don't need every store on the planet to reinvent a custom proprietary wheel to 'solve' a "how to take a screenshot / pause an MP3 player" problem that was solved +25 years ago, and with software that's 100x less bloated than full-fat gaming clients.

Subject 1: No. As outlined by other posts, this isn't as simple as snapping your fingers and making a game compiled for a 640 x 480 resistive touch tablet magically work on mobile devices.

Subject 2: That's hypothetically what Galaxy is for, but more to the point a lot of old world multiplayer relies on protocols and connection types that went extinct in the 2000s.

Subject 3: This is loaded. Hoo boy. SteamOS is a fully integrated Arch based KDE desktop system. It took years of research, a few misfires, and a new paradigm to do what it did. Turning GOG Galaxy into something that even resembles Steam's level of integration would take a lot of work and skilled programmers that I'm not sure live in Poland.

As for being a fully integrated platform, let me go though your itemized list and tell you what I think as an opinionated user.
1) That would not be trivial due to MacOS users. MacOS has a habit of changing the paradigm and there are several games that would need recompiled completely to fit back into things. 1a) Linux systems while having a much larger compatibility window, tend to put their libraries in different places and under different names. I hope you like having to guess which six directory schemes and naming schemes libesl.so is under.
2) That's something GOG missed the boat on, but also is not something they're even equipped for. More to the point, I think voice chat is dreadful, even if it is free.
3) Maybe, but that would imply there are enough multiplayer games to make such a feature worthwhile.
4) Unneeded. Cloud saves are a nice bonus, but only if they're handled artfully. Achievements are just a global wank leaderboard.
5) Maybe, but not all games are modded the same way; some of them have very finicky data structures that must be respected and obeyed, unlike games that have a "DUMP MODS HERE" folder. Plus, GOG would have to get permission of the modders for once in their lives.
6) Redundant and possibly complicated. Just put in a hook to OBS or something.
7) This isn't the 1980s, kid. Nobody gives a [redacted] about score anymore. See my statement about achievements too.
8) Advanced analytics such as...what? You're asking for either a highly invasive program or a magic psychic program. Most games don't make a habit of reporting their activity or broadcasting it. Cosmos's Cosmic Adventure just knows it's running.
9) Redundant. Just use a tool like mangohud or goverlay. Not to mention that most graphics cards software comes with a FPS counter, screen recorder, and other such things built in as free bloat.
10) And how would this be accomplished? Streaming? That won't work; the whole point is to be able play games offline. Directly? Some games use really obscure music formats, or compressed. Sometimes both. Not to mention...isn't the whole point to play games, which themselves will have their own music? Media players is free; just get VLC or something.
11) Now, this might have some validity, but given that most of the goodies come in the form of compressed files, someone would have to host them to be able to preview them.
12) Or maybe they could just make the API and Galaxy itself open source so we could contribute to it as a community.
13) Oh, just one more thing you forgot to mention: What exactly is this hypothetical Galaxy OS/GOG OS supposed to be based on, and who's going to make it?

Thank you all for joining this press conference. I would like to make the following official statement:

NO.

That is all. I will not be taking any questions at this time.

Steam then?