On the official website of this Custom ROM my device has not been mentioned in the Supported Devices , although phones of the same company (Motorola) which were released before my phone (G3 etc.) are said to be compatible.
i wanna ask if it is safe for me to install this Custom ROM on my device and if yes, then what is the procedure.
Thanky You,
Leaper
How do I install lineage os on my Moto G5s?
806 Views Asked by user9912524 AtThere are 3 best solutions below

Safety cannot be guarenteed. Your warranty will be void.
Before you start you need
- A pc with ADB and fastboot
If you want to try it out.
- You need to unlock your bootloader for that you need to botain the unlock key and just run
fastboot oem unlock <unlock code>
- Then you have to flash a custom recovery (eg TWRP) by downloading it from the forms and flash it by
fastboot falsh recovery <recovery file name>
- Then you need to flash the ROM on to your device and also the GAPPS (if you need it)
Links

FYI, I down voted this question because it has nothing to do with programming...
That being said... I just did this procedure and wrote up all the steps in my blog here (this installs lineage 14.1/android 7.1). If you follow that, it should work just fine.
Note that the procedure is far too detailed to answer directly in this post if you are inexperienced with the process of flashing ROMs, hence why I gave the blog link and @jobinrjohnson has already listed the general steps and requirements in the procedure.
You are right, no its not officially supported right now... however, I have used the unofficial builds posted on the xda forums (the most recent one as of posting this, and the same ones referenced in the blog post), and I have had no problems so far after a few weeks of use. It works as good as the official lineage builds as far as I can tell. I would not be surprised to see it get listed on the official lineage list in the coming months.
To install this custom rom for personal use, it is not secure.People use it for testing & devloping purposes.