Just upgraded:
6100 Max - all went fine and took only few minutes.
7100 DT - all went fine, for unknown reason this took nearly 15 minutes. I started to worry significantly, but all looks good.
Interesting things:
a) for the unknown reason on 6100 Max had to do "tailscale login" - otherwise tailscale was not starting. 7100 DT had no troubles and I did not have to do "tailscale login". Both routers have non-expiring keys, so I do not understand 6100 tailscale problem :)
b) I had custom patch applied in 7100 DT (https://forum.netgate.com/topic/183961/nut-package-2-8-1-and-above/58). Reverted it before upgrading, unclicked Auto Apply (it is still uncliked), but this custom patch was re-applied for some reason (?). It had no Auto Apply - I disabled it before uprade. Anyway is it okay to keep this patch? (it was really helpfull with NUT problems)
c) In both upgraded (24.03) routers I see small glitch in Boot Environments. Icon for Diagnostics / Configuration History is missing. See picture kindly.
Button glitch