and, why do you need to connect timescaledb to signoz?

I want to be able to monitor parameters like cpu usage, free hdd space and similar

I think this integration is something specific to them that we do not control. If they were exposing OpenTelemetry format data, then it should be possible.

Let me quickly check if it would be possible to use their Prometheus integration

You should be able to do this by using prometheus integration https://docs.timescale.com/tutorials/latest/monitor-mst-with-prometheus/

# prometheus.yml for monitoring a Timescale Cloud instance
global:
 scrape_interval:     10s
 evaluation_interval: 10s
scrape_configs:
 - job_name: prometheus
   scheme: https
   static_configs:
     - targets: ['{TARGET_IP}:{TARGET_PORT}']
   tls_config:
     insecure_skip_verify: true
   basic_auth:
     username: {ENDPOINT_USERNAME}
     password: {ENDPOINT_PASSWORD}
remote_write:
 - url: "http://{ADAPTER_IP}:9201/write"
remote_read:
 - url: "http://{ADAPTER_IP}:9201/read"

How to enable prometheus receiver at SigNoz https://signoz.io/docs/userguide/send-metrics/#enable-a-prometheus-receiver