This is great news in terms of the server migration, IONOS are...not good.
However I'm concerned at the suggested downtime and that there may be issues to iron out on the new server.
A server migration should have next to zero risk of many post migration issues, and literally zero risk of data loss.
Downtime needn't be any longer than the time it takes to import a fresh database copy, test via hosts file, and change DNS.
Hopefully its just an exaggeration to set expectations in the case of problems!
Im sure its in hand but I love the forum too much to take the risk of saying nothing and it going wrong over saying something and patronisingly repeating the existing plan

Hopefully, that looks like this (some steps simplified!):
LAF stays online until the point noted later.
Create new server instances
Configure basic software which doesn't have a version dependency for SMF (Apache and mysql, and the email service, amongst others, can likely all be current release version).
Configure version specific dependencies which might include mysql and will almost certainly need an older php version. Using Remi repositories and php-fpm its possible and quite easy to run an old version alongside a newer one so that the upgrade to SMF can later be done on the same server.
So by this point we should have a server capable of running the version of SMF that LAF is using.
Add LAF to a git repo (current server).
Take a database export (current server).
Clone the git repo (new server).
Rsync the database from current to new server. (Scp it down to local machine and back up if firewall proves a problem).
Configure the db connection on new server if not already done.
Point local hosts file at new server IP and test.
Probably the most difficult step: Resolve any inevitably missed php extensions etc

And any other obvious server related bugs.
Rsync the media from current to new server.
Retest - it should just work now with all images present etc.
*Only now* is it necessary to put the holding page up on current server.
Reexport, transfer, and import database to capture the last data.
Quickly retest, only basics as little should have changed.
Repoint DNS.
Cancel old server after a suitable paranoia overlap period.
Now, a second instance of the forum can be created on the new server but on the new software version and a parallel php process.
Then a similar process can be used to test and dry-run the forum software update safely without risking the actual forum.
I've helped before and would be more than happy to help again even if just with planning, please just ask.
Godspeed - there's a lot of us who love and rely on this forum!
