Epic Pinball

Commander Keen Dreams
Raptor or Tyrian
Cyberdogs (c-dogs are open source and free)
Liero
Blood
Brutal DOOM
Shadow Warrior
Tempest 2000
Worms
JazzJackRabbit 1 and 2

https://alephone.lhowon.org/games/marathon2.html

Also, there are MANY sites that offers dos games through the browser and only requires a keyboard, f.ex on The Internet Archive, and several others just a search away.

https://archive.org/details/softwarelibrary_msdos_games?and%5B%5D=emulator_start%3A%2Aiafix%2A&sin=&sort=-publicdate

https://archive.org/details/softwarelibrary_msdos_games

https://armorgames.com/category/keyboard-only-games

Two great keyboard-only linux-native games:

Tales of Maj'Eyal:
https://te4.org/download

Cataclysm: Dark Days Ahead
https://cataclysmdda.org/releases/

Stay focused on the topic at hand.

How about some 2D jump'n run games.

Giana’s Return
https://www.gianas-return.de/

Secret Maryo Chronicles
http://www.secretmaryo.org

SuperTux
https://www.supertux.org

One Must Fall 2097. It's an old school fighting game. Arcade mode lets you play a storyline, similar to Street Fighter or Mortal Kombat. Tournament mode lets you fight for money, where you spend it on upgrading your robot, and training your own attributes. I still bob my head to the main song at times.

Here's a video that showcases a few AI matches.

https://www.youtube.com/watch?v=15bvpznQP5M

Hmmm, take a hike!

Rayman Origins
Abe's Oddysee
Race the Sun is pretty chill I suppose, at least initially.

If you have a keyboard with numpad, then by all means get Crusader: No Remorse and No Regret.

I'm fairly certain both Hollow Knight as well as the Steamworld games should all fit the bill. All keyboardable (I'm not 100% on Dig2 and Quest, memory's a bit fuzzy there), native versions, strong games, quite a bit of content. Though I am not entirely sure how chill an experience Hollow Knight is going to be, I think it fits perfectly with the christmas spirit.

It's been ages since I've played them, but I'm pretty sure that's a yes. Although inventory management was a bit fiddly as far as I recall.

Not native, but with official Linux support: FlatOut 1 and 2. Fully playable with keyboard only and really cheap at the moment.

If you're using dosbox it crashes if you try and use an onscreen keyboard without having a real one attached.

An on-screen keyboard won't be helpful in the OP's situation, as they *have* a physical keyboard, but *lack* a pointing device.

With that said, the reverse, which would be helpful, is in fact possible if you have a numeric keyboard. Here's Ubuntu's documentation on this feature:
https://help.ubuntu.com/stable/ubuntu-help/mouse-mousekeys.html.en

This is probably not suitable for games that require real-time aiming, and it probably isn't comfortable to use as your primary means of interaction, but it might be useful if a game is keyboard-accessible except for some issue that only comes up infrequently and not in a real-time segment. (I'm thinking Tangledeep, which is keyboard-accessible except when searching your inventory (a feature that is useful but not mandatory to play the game well), where one might be able to use something like mouse keys to use a virtual mouse for those situations; then again, in a case like this, the proper solution is for the devs to fix their game.)