Thank you again! Here is what happened later:
I begin testing. With current kernel 5.16.16: steam fails from command line “steam” and from Cinnamon menu with “/usr/bin/steam %U”
Plain reboot back into kernel 5.16.16: steam starts from command line. Then I exit. Then I again am unable to start both from console and menu.
Plain reboot back into kernel 5.16.16 again. Successful start from command line. Exit. Start from menu with activated “Open in terminal” option. Terminal output:
steam.sh[2464]: Running Steam on fedora 35 64-bit
steam.sh[2464]: STEAM_RUNTIME is enabled automatically
setup.sh[2540]: Steam runtime environment up-to-date!
steam.sh[2464]: Steam client's requirements are satisfied
[2022-03-28 22:36:02] Startup - updater built Mar 14 2022 19:48:46
Installing breakpad exception handler for appid(steam)/version(1647446817)
[2022-03-28 22:36:02] Loading cached metrics from disk (/home/ssr/.local/share/Steam/package/steam_client_metrics.bin)
[2022-03-28 22:36:02] Using the following download hosts for Public, Realm steamglobal
[2022-03-28 22:36:02] 1. https://cdn.cloudflare.steamstatic.com, /client/, Realm 'steamglobal', weight was 100, source = 'update_hosts_cached.vdf'
[2022-03-28 22:36:02] 2. https://cdn.akamai.steamstatic.com, /client/, Realm 'steamglobal', weight was 100, source = 'update_hosts_cached.vdf'
[2022-03-28 22:36:02] 3. http://media.steampowered.com, /client/, Realm 'steamglobal', weight was 1, source = 'baked in'
Installing breakpad exception handler for appid(steam)/version(1647446817)
[2022-03-28 22:36:02] Verifying installation...
[2022-03-28 22:36:02] Verification complete
Loaded SDL version 2.0.21-7140709
/home/ssr/.themes/Adapta-Nokto/gtk-2.0/common-dark.rc:1425: error: unexpected identifier 'direction', expected character '}'
/home/ssr/.themes/Adapta-Nokto/gtk-2.0/3rd-party-dark.rc:475: error: invalid string constant "toolbar", expected valid string constant
At this point steam keeps silent and not running more. I close terminal. Again to command line and type “/usr/bin/steam %U”. Successful start. Exit. Run with “steam” - success. Exit. Again I go to menu. Unable to start from menu. Again stops on “expected valid string constant”. Summary: runs from command line, doesn’t run from menu.
Plain reboot back into kernel 5.16.16 again. Successful start from command line. Exit. Start from menu: failure.
Now I see that initial error - exit after “Steam client’s requirements are satisfied” - is diplayed in console when another process is running that hangs on “expected valid string constant”. I kill steam process. Console start works then.
Plain reboot back into kernel 5.16.16 again. Start from menu: failure. Kill process. Start from console: success.
Appears to be related to Cinnamon menu.
When failure, it stops on:
/home/ssr/.themes/Adapta-Nokto/gtk-2.0/3rd-party-dark.rc:475: error: invalid string constant "toolbar", expected valid string constant
When success, the next string is:
steamwebhelper.sh[5884]: Runtime for steamwebhelper: defaulting to /home/ssr/.local/share/Steam/ubuntu12_64/steam-runtime-heavy
steamwebhelper.sh[5884]: glibc >= 2.34, partially disabling sandbox until CEF supports clone3()