So, no one will be able to tell you if LEDE will work well on your router, or not.
It depends on what your goals are, and how you want to use it.
The LEDE firmware that is available for the DGN3500 and DGN3500B is on the stable release.
I would suggest the following...
Read over the LEDE Quick Start Guide...
https://lede-project.org/docs/guide-quick-start/start
Read over the LEDE User Guide...
https://lede-project.org/docs/user-guide/start
Make sure it's something you want to take on.
LEDE does need to be configured, more so than stock firmware...it is not plug and play.
Often, settings that are not configured correctly cause more issues than not. Becoming familiar with LEDE beforehand is helpful in avoiding that.
Also, make sure you know how to revert back to stock firmware in case things go wrong.
Understand what "failsafe mode" is, what a TFTP recovery is, what a serial recovery is, and when you need to do what.
Bottom line, do your preparation, but in the end, you need to install it and set it up to find out.