I have UniFi at home and still use Pivpn. It's just that much easier with OpenVPN on mobile devices. Highly recommend Pivpn and Pihole in a Pi.
Pivpn is great, but no longer maintained. I still use it though.
As for running a VPN on a synology or qnap... I am not exposing a device that has backups of all my sensitive stuff to the internet. If you must run a VPN on your nas, stick it in a docker container or a VM.
Someone did takeover and it's maintained again.
