Slow boot after upgrade to OSX 10.13.6

Upgraded earlier this week as invited by Apple to 10.13.16 on two very fast SSD machines (iMac and MacBook Pro). Both now are very slow to boot. After picking login ID, get the progress bar sort of “stuck” at about 60% (approx) doing whatever. Overall boot now takes about 5 minutes.

That can’t be right. Anyway to resolve?

Safe Mode may help clear it up:

I’d also try resetting the NVRAM: