• Yes, is on dedicated server, with internet - new docker images are pulling (pruned all your local images).
• Sure, problem exists on fresh docker-compose place
• Yes, tested before send message [STEAM_UID 1000 - STEAM_GUID 1000] uid=1000(user) gid=1000(user) groups=1000(user),999(docker)

Tried to recognize where is a problem and I think is in steamcmd image.

I do some additional tests, problem occur only one machine - maybe my host is banned to download some packages? How can I test it?

valheim_1 | [Valheim][steam]: Running Install...
valheim_1 | [ODIN][DEBUG] - Debugging set to true
valheim_1 | [ODIN][DEBUG] - Debug mode enabled!
valheim_1 | [ODIN][DEBUG] - Launching install command...
valheim_1 | [ODIN][DEBUG] - Env var default 'ODIN_WORKING_DIR': '/home/steam/valheim'
valheim_1 | [ODIN][INFO] - Installing 896660 to /home/steam/valheim
valheim_1 | [ODIN][DEBUG] - Env var default 'ODIN_WORKING_DIR': '/home/steam/valheim'
valheim_1 | [ODIN][INFO] - steamcmd found in path
valheim_1 | [ODIN][DEBUG] - Launching install command: "/usr/bin/steamcmd" "+login anonymous" "+force_install_dir /home/steam/valheim" "+app_update 896660" "+quit"
valheim_1 | [ODIN][INFO] - Exited with http code: 1
valheim_1 | cp: cannot stat '/home/steam/steamcmd/linux64/steamclient.so': No such file or directory
valheim_1 | [Valheim][steam]: Initializing Variables....
valheim_1 | [ODIN][DEBUG] - Debugging set to true
valheim_1 | [ODIN][DEBUG] - Debug mode enabled!
valheim_1 | [ODIN][DEBUG] - Launching configure command...
valheim_1 | [ODIN][DEBUG] - Pulling config file...
valheim_1 | [ODIN][DEBUG] - Env var found 'ODIN_CONFIG_FILE': '/home/steam/valheim/config.json'
valheim_1 | [ODIN][DEBUG] - Config file set to: /home/steam/valheim/config.json
valheim_1 | [ODIN][DEBUG] - Writing config file...
valheim_1 | [ODIN][DEBUG] - Env var default 'ODIN_WORKING_DIR': '/home/steam/valheim'
valheim_1 | [ODIN][DEBUG] - Checking env for server_executable
valheim_1 | [ODIN][ERROR] - Failed to find server executable! Please run odin install

Huh, while the server is running the container try accessing it via:

docker-compose exec valheim bash

and then in the container:

gosu steam bash

Once as the steam user, try running:

odin install

See if it gives you some grief running manually

I can mark as solved. A problem was in libcurl. Why? Because Debian 9.13 (marked as oldstable and with support until 06.2022) was update blocker for docker engine >19.03. So i Manually upgrade my distro to Debian Buster (10) and docker-ce to 20.10 and.. now it working as intended. Anyway, put info about docker engine version - supporting only Docker >=20

Your image was a first that exposed me a problem with docker hosting machine.