@MartinLangmaid, @mldowling, @Rick-DC and other fellow partners 
As promised by Engineering team, the test firmware for LAN NTP server feature is ready for partner. You can download the test firmware using the followings URL:
As for now , the test firmware is only available for the below device models that having RTC Chipset (RTC - Battery powered time storage to keeps time running even router is power off.):
NTP Server Test firmware (8.0.2s052):
Balance One/Balance 210hw4/Balance 310/MAX BR1 ENT/MAX Transit/MAX 700hw3/MAX HD2 mini/MAX HD4(Edited : 21/02/2020):
https://download.peplink.com/firmware/plb1/fw-b1_210hw4_310hw4_br1ent_transit_m700hw3_hd2mini_hd4-8.0.2s052-build4438.bin
B210_310hw2hw3(Edited : 21/02/2020):
https://download.peplink.com/firmware/plb310/fw-b210_310_hw2_hw3-8.0.2s052-build3672.bin
B305hw2/B380hw6/B580hw2/B710hw3/B1350hw2/B2500(Edited : 21/02/2020):
https://download.peplink.com/firmware/plb2500/fw-b305hw2_380hw6_580hw2_710hw3_1350hw2_2500-8.0.2s052-build2747.bin
EPX/SDX/MBX (Edited : 21/02/2020):
https://download.peplink.com/firmware/epx/fw-epx_mbx_sdx-8.0.2s052-build1438.bin
SpeedFusion Engine Cam (Edited : 24/02/2020):
https://download.peplink.com/firmware/plb1/fw-b1_210hw4_310hw4_br1ent_transit_m700hw3_hd2mini_hd4-8.0.2s052-build4438.bin
For the above firmware, default NTP server is enabled for the device LAN interface. As for now, we have no WebUI that allow to enable/disable the feature. If the feedback from our fellow partners is good, then the feature will be roll out for the next general release firmware including the option to enable/disable the NTP Server service.