We did this in 2023, my best advice is to ignore the salespeople and demand to talk to engineers BEFORE your cutover date. The salespeople really have no idea what the heck they are talking about.
In our situation, our internal domain is not publicly addressable, and we were told repeatedly that this would not be an issue by the sales and support staff. I was very confused that this would not be an issue but trusted them. Migration date comes and I am talking to the engineer, and in the first 5 minutes we are told this non publicly addressable domain will be an issue and a massive one at that as we needed to go open internet. In the end we had to wipe and load the entire fleet.
If you are migrating you're existing Jamf instance to Jamf Cloud, you need to setup a CNAME redirect to "trick" your devices that the new Jamf server is the old Jamf server. If you want to be open internet, whatever your servers URL is needs to be publicly addressable now, if it's not then the Jamf Cloud server will not be publicly addressable either.
Other than that, the engineer that worked with us was amazing and went well above and beyond to make sure we were buttoned up as best as could be done. Nearly 2 years in, and I have no regrets once so ever, and I am actually thankful we effectively restarted the environment as it allowed us to clear out a lot of tech debt.
