Prepping for an expected FTTP install & I'm not willing to take a chance on the 2136 yet until MultiNAT arrives so I'm temporarily going to replace my trusty 2860Vac with a 2866ax from eBay. 

Can anyone confirm if I'll simply be able to restore a backup on the newer model or will the absence of VOIP & addition of WiFi 6 cause me headaches?
 

How fast is the FTTP connection?

I found a 2860 quite good enough for a 150Mb/s fibre connection?

I would guess a 2860 would be good enough for around 200Mb/s perhaps even 300Mb/s.

 

I'm getting close to 150Mbit on my current FTTC install & the 2860 needs to be rebooted on a schedule a couple of times a week. If I don't, it becomes unstable, the GUI locks up and eventually data stops flowing altogether, even though I'm using the external BT modem for the connection itself.  If I turn hardware acceleration on or make certain firewall changes, the situation gets worse.
For FTTP, Openreach are still testing as they only pulled the fibre at the start of the month so they haven't confirmed speeds but BT Wholesale say that FTTP on Demand would be at least 330Mbit.

Maybe the 2860 would continue to be okay short term (I had toyed with trying) but I really didn't want to be in a position where I needed to move quickly to rectify a problem as I'd then either need to pay through the nose or accept a loss of functionality. An option for a cheap 2866ax arose & I took it - I'll flip it on eBay if / when the 2136 gets MultiNAT - that functionality is the dealbreaker for me.

I assume your current setup is

My 2860 (which had a config migrated from a 2820) was rock solid on VDSL and never locked up.

Personally I would build the config on your 2866 from scratch rather than transfer it as I wonder if the crash and the config are related.

I did that rebuild moving to a 2927 and I screenshotted each config page and recreated it that way..

I moved from a 2850 to my 2860 & built it the same way as you at the time (I have a feeling that I couldn't restore due to different firmware versions but I'm trying to be lazy here.

Maybe I'll just give the restore a go & if I see anything wrong at all, factory reset & type everything in.  I know that I can export my LAN IP to MAC and IP Object settings to csv but it's the rest of the object stuff, NAT, Firewall & LAN DNS stuff that I really can't be bothered to type in if I can help it. 

Pretty certain that my stability issues are the hardware starting to fail as I've got some scorching on the case where something's obviously been quite hot inside - I've had 9 good years out this whereas I only got 4 out of the 2850 before I had to update it due to throughput limitations then I got another 4 or 5 using it as an AP before its hardware went.