This is a report for "Steam for Linux" but this morning I was told the same thing happens in the client for Windows!

Your system information

• Steam client version (build number or date): 1.0.0.82-2
• Distribution (e.g. Ubuntu): Arch
• Opted into Steam client beta?: [Yes/No] No
• Have you checked for system updates?: [Yes/No] Yes
• Steam Logs: [generate by running this command in a terminal tar -zcvf ~/Desktop/steam-logs.tar.gz ~/.steam/steam/logs] Unfortunately none. This problem happened yesterday. The youngest log is from August 3rd.
• GPU: Nvidia/Intel/AMD - nvidia RTX 3070 Ti

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

Last night I was playing "Mad Max". While I was playing it, a new update for "Titan Quest 2" appeared and "Mad Max" crashed. I had to kill its process using killall in order to close it, nothing else would help. After that I ran "MM" again but it crashed in the menu.
After I allowed "TQ2" to update, the crashes stopped.

This isn't the first such a crash happens when another game has an update waiting. The first two times it happened I thought I had pressed something that I shouldn't but after "Mad Max" (the native Linux version) crashed while I was hanging at a balloon without touching any keys, I'm pretty sure the cause of these crashes is when an update for a game is released and is waiting to be downloaded.
Ever since I bought "Mad Max" (2015 or 2016 - I don't remember when exactly) I've never had a single crash of the game, until now.

I've set the client not to download/update anything while I'm playing a game, so thus must be a bug in the steam client.

What happened: while playing a game an update for another game in the library is released and the currently played game crashed.
What shouldn't happen: currently played game shouldn't crash when an update for another game appears.

Steps for reproducing this issue:

1. Install "Titan Quest 2" (this is the newest games, therefore updates arrive pretty much every day).
2. Run any game, "Mad Max" for instance, and start playing it.
3. If you're lucky enough for a TQ2 update to be released while you're playing, "Mad Max" will crash.

P.S. The user Brynvagn said he's noticed the same behavior in the topic I posted in the steam community: https://steamcommunity.com/app/221410/discussions/0/802322896293800767/