Thank you very much to Pavel for the curl issue. I had to re-install curl and libcurl from LEDE repo and not Onion repo to get 7.54.1 (from Onion I got 7.52.1), but that,s not solved the issue another package was missing "ca-bundle".
After opkg install curl libcurl ca-bundle all is fine for curl.

Regarding to the current issue, thanks to ccs_hello. I guess you're right with the curret inrush explanation, but the issue is present only when Omega2+ is on battery, when alimentation is from micro-usb all seems to be ok. The same when i reboot the Omega2+ on battery with the USB stick already plugged. Then it's not a "show stopper" issue because this stick that made gateway between the "z-wave network" will be always plugged in. Just weird to see the different reactions of Omega2+

Finally, thanks again to css_hello, I understand that the USB-serial driver is "built-in"Omega2+ firmware because the device ttyACM0 is created when stick is plugged in, but the upper-half of the driver (the z-wave part) is supposed to be complied against Domoticz. Perhaps a incompatibility with packages compiled against Domoticz and some others compiled against Omega2+. May be I had to try to recomplie the Openzwave driver on Omega2+.

@Mark-Williams May be using an already existing home automation product supported on LEDE like Domoticz ? It can be accessed from outside of your LAN and already have an Android App. By creating virtual device associated with scripts you'll be able to control GPIO

As a user of Domoticz since several month I have my primary controller for home automation installed on a Synology NAS.

I have two sticks to control my sensors and switches, a ZW090 Z-Wave stick and a RFXCOM RFXtrx433E.

Since Domoticz is supported on LEDE and Omega2+ is a derivation of LEDE I tried to make it operationnal.

Followed steps :

1. Be sure to have latest firmware
   oupgrade -c
   1.1 If not, then upgrade firmware
   oupgrade
2. Be sure to have latest packages list
   opkg update
3. Install curl because I need it in some of my Domoticz shell
   opkg install curl
4. Get access to genuine LEDE repo by editing /etc/opkg/distfeeds.conf as documented in Onion Omega2 documentattion [https://docs.onion.io/omega2-docs/using-opkg.html]
5. reboot and update package list
   reboot
   opkg update
6. Install Domoticz
   opkg install domoticz
7. reboot

Domoticz starts and is accessible via http://<your ip address>:8080

But I now faced three issues :

• Usage of curl with https:// site gives error (77). No error with sites without SSL (http://)

• When plugging ZW090 usb Z-wave stick on Powerdock usb connector on a running Omega2+ system powered on battery, it crashes and I have to reboot it.
  When ZW090 is plugged before system starts it seems to works and devive /dev/ttyACM0 is created (on the same battery powered system).

• OpenZwave driver error when trying to add ZW090 controller to Domoticz
  Plugged Aeon Labs Aeotec Z-Wave Z-Stick (ZW090). Seems to be recognized by Omega2+ by adding /dev/ttyACM0 but can't add it in Domoticz Hardware. Log says "Openzwave driver failed!". But I can't figure out where to look for the origin of this issue (missing module in OS, missing package in opkg or trouble with Domoticz LEDE package on Omega2+ modified LEDE OS)

Any suggestions ?