One can love the game so much to have its pocket version.
https://www.gog.com/en/games/osx
and https://www.gog.com/en/games/linux
https://www.gog.com/en/games/windows

There are PC games in our store that are available for Android, mainly from the Play Store.

Anomaly.apk
Bad North.apk
Baldur's Gate.apk
Baldur's Gate 2.apk
Mini Metro.apk
Planescape Torment.apk
Thronebreaker.apk
Worms 3.apk

Do you know any more games available here and for Android?
Edit: thank you!✨

There is the 2 Star Wars KOTOR

Sourceports are fun. You can play games like Broken Sword, Indiana Jones and Monkey Island with ScummVM on Android. There's also VCMI, which lets you play Heroes of Might and Magic 3.

I believe there are some dosbox apps for Android so if you feel like porting some of your GOG library over, you can probably do that.

There's also a couple of Amiga emulators for Android, so if you have the .adf files of some oldies (and some kickstart ROMs) you can also run them on your smartphone. For many games, the Amiga versions were way better than the MS-DOS counterparts sold on GOG.

(I still think GOG should have embedded some Amiga versions in emulators like they managed to do with dosbox. But that's a wholly different can of worms.)

Both Talisman games (Digital Edition and Origins) are available on Android.

the Reigns games the Kingdom games, Vampire's Fall origins, many Android ports, I'm saving this page to add them as I find them. Be careful mentioning the P* Store as it might get your thread locked.

Stardew Valley is on Android.

I'd suggest to follow the Publishers track. Some to mention below.
I hope helps and this thread contributes to build an exhaustive list.

Disclaimer colored in blue
Any brand/publisher/store/TM mentioned on this post is solely for informative purposes.
I explicitly declare this: It is NOT for any advertising, referral or profit purposes.
Therefore, any GOGs BS censoring/deleting/editing/banning this post/author/thread runs on GOGs own shame, legal-responsibility and arbitrary-discretional-interpretational-enforcement of the GOG forum rules they change at any time at their own convenience without notifying us (the users).
(I KNOW IT IS A VERY IMPOSSIBLE REQUEST FOR GOG, BUT HERE IT GOES:
IF ANY DOUBT, QUESTION, CONCERN - CONTACT ME TO DIALOG BEFORE ANYTHING!)

*Others from 11 bit studios:
-Anomaly Korea
-Anomaly Warzone
-Spacecom
-This War of Mine

*Others from Beamdog
-Axis & Allies 1942 Online
-Icewind Dale: Enhanced Edition
-Neverwinter Nights: Enhanced Edition
-Planescape: Torment: Enhanced Edition

*Team17 Digital LTD
-Sheltered
-The Escapists 2: Pocket Breakout
-Worms: Armageddon

*CDPR
-GWENT: The Witcher Card Game

*DevolverDigital:
-Downwell
-GRIS
-Minit
-My Friend Pedro
-Reigns
-Reigns: Her Majesty
-Reigns: Game of Thrones
-Shadow Warrior Classic Redux
-The Talos Principle

*505 Games
-Brothers: A Tale of Two Sons

*Amanita Design
-CHUCHEL
-Machinarium
-Samorost 1
-Samorost 2
-Samorost 3

*Annapurna Interactive
-Florence
-Gorogoa

*Asmodee Digital
-A Game of Thrones: The Board Game
-Carcassonne
-Terraforming Mars
-Ticket to Ride

*Blue Brain Games
-The House of Da Vinci
-The House of Da Vinci 2

*Headup
-Bridge Constructor (several)
-Dead Age
-The Inner World
-Trüberbrook
...

*inkle Ltd
-80 Days
-Overboard!

*Ironhide Game Studio
-Iron Marines
-Kingdom Rush Origins
-Kingdom Rush Vengeance
-Kingdom Rush Frontiers

*Kaigan Games OÜ
-SIMULACRA
-SIMULACRA 2

*Rusty Lake
-Rusty Lake
-Rusty Lake Paradise
-Rusty Lake: Roots
-The White Door

*Square Enix
-Life is Strange
-Life is Strange: Before the Storm

*Telltale
-Batman: The Enemy Within
-Batman - The Telltale Series
-The Wolf Among Us

*Microids ==> Anuman
-Agatha Christie - The ABC Murders
-Syberia
-Syberia 2

*Raw Fury
-Dandara
-Kathy Rain
-Kathy Rain: Director's Cut
-Kingdom Two Crowns
-Kingdom: New Lands
-The Longest Road on Earth
-Townscaper
-Whispers of a Machine

*Motion Twin // Shiro Games // Rain Games // Merge Games, Maple Whispering Limited // Weather Factory ==> Playdigious
-Cultist Simulator
-Dead Cells
-Evoland
-Evoland 2
-Northgard
-Sparklite
-Streets of Rage 4
-Teslagrad

*Several ==> Noodlecake
-Absolute Drift
-realMyst
-Riven: The Sequel to Myst

*Other:
-OpenTTD
-Dragon's Lair
-Agent A: A puzzle in disguise
-Don't Starve
-Her Story
-Lumino City
-Never Alone
-Oxenfree
-Terraria
-The Silent Age
-World of Goo

*Not GOG but memorable mentions:
-GTA Series (3, VC, LCS, SA, CW)
-Bully
-The Room Series
-Battleheart Legacy
-The Bonfire: Forsaken Lands

Heads up: the versions listed are only either the versions I bought or that I could easily check with a Google search. It's very likely I missed quite a few versions, specially for the games that turn out to be on Play Store.

Aquaria had a DRM free APK version available as part of a past bundle from Humble Bundle. Sadly it was never made available again after that bundle. Also the game only works in older versions of Android, from what I read.

Braveland Pirate and Braveland Wizard also have DRM free APK versions available for purchase.

Someone also ported the original version of Cave Story, from which the Nicalis version derivates, to Android. And if I remember correctly, the author of the original game was fine with fan ports of the game.

Ittle Dew also has a DRM free APK version.

Knights of Pen & Paper +1 also has an Android version, although it seems to be a Play Store exclusive (so most likely DRM'd).

Little Nightmares had an Android remake (also Play Store exclusive). Does that count?

Anodyne also has an Android version (both as a DRM free APK and at Play Store).

SNK's Blazing Star, Fatal Fury Special, Garou: Mark of the Wolves, Metal Slug 1, 2. 3 and X and Samurai Showdown II also have DRM free APK versions.

Oh...Sir!! The Insult Simulator has a Play Store version.

Neurovoider has some prototype Android versions over on Steam, which come as DRM free APKs.

And lastly, it would be nice if the games with DRM free APK versions had more visibility (GOG release, maybe?)

The Oddworld series of games is on the android google play store as well.

Back in 2016 there was a Gogmix created that listed all Gog titles that had Android version. The Gogmixes may be gone but the thread for submitting new titles still exists. Check it out to get a whole bunch of games discovered that have Android versions.

https://www.gog.com/forum/general/gogmix_for_android_community/page1

Cat QUest games

Looks like Galaxy of Pen and Paper also has a Play Store release. Another option if GOG ever sells DRM free APKs, maybe?