Single RDS with local profiles migration to Farm with FSlogix container

Question

SETUP
Old single RDSH 2008 (NO roaming profile or UDP)
New Farm with 2 RDSH 2019 and FSLogix containers (profile and O365 on Refs share on file server)

Question
How to copy the local profiles from the old server and paste them in the containers. Trying to figure out how to do this

My current way, but much tooo long:
Login on new farm with UserA, cmd elevated, DiskMGMT.msc, assign letters to both containers
from that same session browse to \oldrds\c$\users\userA\ as domain admin
copy all desktop, docs, Appdata folders to the profile container

also tried:
copy profiles like UserB to a RDSH on the new farm and login on that server using UserB, but then FSlogix says oh no there already is an local profile... can't I just tell FSLogix to move that local profile in userB's fslogix containers????

so there must be a easier way... surely