I forgot to add --skip-letsenrypt when first running migrate after successful dry runs. SOURCE has certbot, TARGET has acme.sh. Should I now just remove the directory tree /etc/letsencrypt? Then manually turn on Letse encrypt in each websites settings?
Yes, you'll have to remove the /etc/letsencrypt folder. But it might be that your apache or nginx server will be offline after you changed the first website, in this case, delete all symlinks for websites (but not ispconfig and apps vhost) in /etc/apache2/sites-enabled/ (or its nginx equivalent) and then restart web server so it is online again. The reason why it will likely be offline is that symlinks are used for certbot LE certs and by removing the targets of the symlinks, apache will fail to load the vhosts.
Apache was working. I just stopped apache, removed letsencrypt folder and the symlinks starting with 100-* and started apache back. Thanks.