Should your command have a closing double quote? Like:
su akkoma -s $SHELL -lc "./bin/pleroma start"
?
I did that and I got the following dump.
02:42:16.923 [notice] :alarm_handler: {:set, {:system_memory_high_watermark, []}}
02:42:17.460 [error] Use `RUM` index is enabled, but were not applied migrations for it.
If you want to start Pleroma anyway, set
config :pleroma, :database, rum_enabled: false
Otherwise apply the following migrations:
`mix ecto.migrate --migrations-path priv/repo/optional_migrations/rum_indexing/`
02:42:17.461 [notice] Application pleroma exited: exited in: Pleroma.Application.start(:normal, [])
** (EXIT) an exception was raised:
** (Pleroma.ApplicationRequirements.VerifyError) Unapplied RUM Migrations detected
(pleroma 3.4.0-0-gf91b89673) lib/pleroma/application_requirements.ex:32: Pleroma.ApplicationRequirements.handle_result/1
(pleroma 3.4.0-0-gf91b89673) lib/pleroma/application.ex:55: Pleroma.Application.start/2
(kernel 8.3.2.1) application_master.erl:293: :application_master.start_it_old/4
[os_mon] memory supervisor port (memsup): Erlang has closed
02:42:17.474 [notice] :alarm_handler: {:clear, :system_memory_high_watermark}
[os_mon] cpu supervisor port (cpu_sup): Erlang has closed
{"Kernel pid terminated",application_controller,"{application_start_failure,pleroma,{bad_return,{{'Elixir.Pleroma.Application',start,[normal,[]]},{'EXIT',{#{'__exception__' => true,'__struct__' => 'Elixir.Pleroma.ApplicationRequirements.VerifyError',message => <<\"Unapplied RUM Migrations detected\">>},[{'Elixir.Pleroma.ApplicationRequirements',handle_result,1,[{file,\"lib/pleroma/application_requirements.ex\"},{line,32}]},{'Elixir.Pleroma.Application',start,2,[{file,\"lib/pleroma/application.ex\"},{line,55}]},{application_master,start_it_old,4,[{file,\"application_master.erl\"},{line,293}]}]}}}}}"}
Kernel pid terminated (application_controller) ({application_start_failure,pleroma,{bad_return,{{'Elixir.Pleroma.Application',start,[normal,[]]},{'EXIT',{#{'__exception__' => true,'__struct__' => 'Elixir.Pleroma.ApplicationRequirements.VerifyError',message => <<"Unapplied RUM Migrations detected">>},[{'Elixir.Pleroma.ApplicationRequirements',handle_result,1,[{file,"lib/pleroma/application_requirements.ex"},{line,32}]},{'Elixir.Pleroma.Application',start,2,[{file,"lib/pleroma/application.ex"},{line,55}]},{application_master,start_it_old,4,[{file,"application_master.erl"},{line,293}]}]}}}}})
Crash dump is being written to: erl_crash.dump...done