Установленные пакеты:

- prometheus-3.5.0-alt1.x86_64
- python3-module-prometheus-pve-exporter-3.4.1-alt1.noarch

Система обновлена:

# cat /etc/os-release 
NAME="ALT Server"
VERSION="11.1"
ID=altlinux
VERSION_ID=11.1
PRETTY_NAME="ALT Server 11.1 (Mendelevium)"
ANSI_COLOR="1;33"
CPE_NAME="cpe:/o:alt:server:11.1"
BUILD_ID="ALT Server 11.0"
ALT_BRANCH_ID="p11"
HOME_URL="https://basealt.ru/"
BUG_REPORT_URL="https://bugs.altlinux.org/"
DOCUMENTATION_URL="https://docs.altlinux.org/"
SUPPORT_URL="https://support.basealt.ru/"
VARIANT_ID=edition_server
VARIANT="ALT Server"
LOGO=alt-server-logo

В момент запуска всё ОК:

# systemctl status prometheus-pve-exporter.service
● prometheus-pve-exporter.service - Prometheus Proxmox VE Exporter
     Loaded: loaded (/usr/lib/systemd/system/prometheus-pve-exporter.service; disabled; preset: disabled)
     Active: active (running) since Wed 2025-10-22 16:41:18 MSK; 18ms ago
 Invocation: 778ec58056284515a43135e29e1e918d
       Docs: https://github.com/prometheus-pve/prometheus-pve-exporter
   Main PID: 1850 ((exporter))
      Tasks: 1 (limit: 4679)
     Memory: 0B (peak: 0B)
        CPU: 0
     CGroup: /system.slice/prometheus-pve-exporter.service
             └─1850 "(exporter)"

окт 22 16:41:18 grafana.kou.alt systemd[1]: prometheus-pve-exporter.service: Scheduled restart job, restart counter is at 1.
окт 22 16:41:18 grafana.kou.alt systemd[1]: Started prometheus-pve-exporter.service - Prometheus Proxmox VE Exporter.

Через несколько секунд:

# systemctl status prometheus-pve-exporter.service
× prometheus-pve-exporter.service - Prometheus Proxmox VE Exporter
     Loaded: loaded (/usr/lib/systemd/system/prometheus-pve-exporter.service; disabled; preset: disabled)
     Active: failed (Result: exit-code) since Wed 2025-10-22 16:41:20 MSK; 722ms ago
   Duration: 311ms
 Invocation: d96743be024241308e2b808421879993
       Docs: https://github.com/prometheus-pve/prometheus-pve-exporter
    Process: 1856 ExecStart=/usr/bin/pve_exporter /etc/prometheus/pve.yml (code=exited, status=2)
   Main PID: 1856 (code=exited, status=2)

окт 22 16:41:20 grafana.kou.alt systemd[1]: prometheus-pve-exporter.service: Scheduled restart job, restart counter is at 5.
окт 22 16:41:20 grafana.kou.alt systemd[1]: prometheus-pve-exporter.service: Start request repeated too quickly.
окт 22 16:41:20 grafana.kou.alt systemd[1]: prometheus-pve-exporter.service: Failed with result 'exit-code'.
окт 22 16:41:20 grafana.kou.alt systemd[1]: Failed to start prometheus-pve-exporter.service - Prometheus Proxmox VE Exporter.

В логах службы ошибка: pve_exporter[1856]: pve_exporter: error: unrecognized arguments: /etc/prometheus/pve.yml

Изучил systemd-юнит, нашёл решение: 
Файл /etc/systemd/system/prometheus-pve-exporter.service.d/override.conf с содержимым:

[Service]
ExecStart=
ExecStart=/usr/bin/pve_exporter --config.file /etc/prometheus/pve.yml

После чего служба корректно работает без падения. Не хватает указания --config.file