Application Icon does not work for Linux

[Fl4m3Ph03n1x]

When launching the application, on the left panel, the application has no icon:

How I launched the app:

• enter assets folder
• npm install
• cd ..
• mix assets.deploy
• ./run

No visible errors are shown:

$ ./run 
Erlang/OTP 24 [erts-12.1.5] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

warning: use Mix.Config is deprecated. Use the Config module instead
  config/dev.exs:1


12:05:52.202 [info]  Application eex started at :nonode@nohost
 
12:05:52.208 [info]  Application mime started at :nonode@nohost
 
12:05:52.208 [info]  Child Agent of Supervisor Plug.Crypto.Application started
Pid: #PID<0.283.0>
Start Call: Agent.start_link(#Function<0.16488927/0 in Plug.Crypto.Application."-fun.start_crypto_keys/0-">)
Restart: :permanent
Shutdown: 5000
Type: :worker
 
12:05:52.211 [info]  Application plug_crypto started at :nonode@nohost
 
12:05:52.213 [info]  Child :telemetry_handler_table of Supervisor :telemetry_sup started
Pid: #PID<0.288.0>
Start Call: :telemetry_handler_table.start_link()
Restart: :permanent
Shutdown: 5000
Type: :worker
 
12:05:52.213 [info]  Application telemetry started at :nonode@nohost
 
12:05:52.214 [info]  Child Plug.Upload of Supervisor Plug.Application started
Pid: #PID<0.293.0>
Start Call: Plug.Upload.start_link([])
Restart: :permanent
Shutdown: 5000
Type: :worker
 
12:05:52.215 [info]  Application plug started at :nonode@nohost
 
12:05:52.216 [info]  Child :pg of Supervisor #PID<0.297.0> (Supervisor.Default) started
Pid: #PID<0.298.0>
Start Call: :pg.start_link(Phoenix.PubSub)
Restart: :permanent
Shutdown: 5000
Type: :worker
 
12:05:52.216 [info]  Application phoenix_pubsub started at :nonode@nohost
 
12:05:52.216 [info]  Application phoenix_view started at :nonode@nohost
 
12:05:52.222 [info]  Child Phoenix.CodeReloader.Server of Supervisor Phoenix.Supervisor started
Pid: #PID<0.304.0>
Start Call: Phoenix.CodeReloader.Server.start_link([])
Restart: :permanent
Shutdown: 5000
Type: :worker
 
12:05:52.222 [info]  Child Phoenix.Transports.LongPoll.Supervisor of Supervisor Phoenix.Supervisor started
Pid: #PID<0.305.0>
Start Call: DynamicSupervisor.start_link([name: Phoenix.Transports.LongPoll.Supervisor, strategy: :one_for_one])
Restart: :permanent
Shutdown: :infinity
Type: :supervisor
 
12:05:52.222 [info]  Application phoenix started at :nonode@nohost
 
12:05:52.235 [info]  Child Gettext.ExtractorAgent of Supervisor #PID<0.309.0> (Supervisor.Default) started
Pid: #PID<0.310.0>
Start Call: Gettext.ExtractorAgent.start_link([])
Restart: :permanent
Shutdown: 5000 
Type: :worker
 
12:05:52.235 [info]  Application gettext started at :nonode@nohost
 
12:05:52.250 [info]  Child :disk_log_sup of Supervisor :kernel_safe_sup started
Pid: #PID<0.311.0>
Start Call: :disk_log_sup.start_link()
Restart: :permanent
Shutdown: 1000
Type: :supervisor
 
12:05:52.250 [info]  Child :disk_log_server of Supervisor :kernel_safe_sup started
Pid: #PID<0.312.0>
Start Call: :disk_log_server.start_link()
Restart: :permanent
Shutdown: 2000
Type: :worker
Sass is watching for changes. Press Ctrl-C to stop.

[watch] build finished, watching for changes...
[notice] Connecting to UNIX socket: "/run/user/1000/bus"

[notice] DBUS auth: sending initial data

[notice] Got GUID '027f216ba8c2148b5e89683862860b5f' from the server

[notice] Succesfully negotiated UNIX FD passing

[notice] Calling "/"::"org.freedesktop.DBus".:Hello([])

My system specs:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.4 LTS
Release:        20.04
Codename:       focal