Daughter's mortgage was turned down last minute purely because of an absentee freeholder. So yes, it can be a major issue, but I guess a lot will depend on the lender and how cautious they are. At the time, they were apparently looking for any reason NOT to,lend.
We were going halves with her on the purchase, and instead ended up buying the whole thing.
Our freeholder was not actually absent, merely hiding a few miles away under another name, presumably because of debts attached to the FH. But I didn't find this out (used a tracing service) until after we'd completed. The solicitor we used had advised us very late in the day not to go through with the purchase, because of the FHolder problem.
However we went ahead, planning to buy the FH later, which we did.
The property is one of 2 maisonettes. The owner of the other decided to sell while we were still going through the process of buying the FH. Her buyer needed to know the freeholder situation - presumably for their lender - and all we could say was that it was going through the court system, which seemed to satisfy them.
If you have a truly absentee freeholder, then the price of the freehold will be worked out by a formula, and then go through due tribunal and. court process. It's actually fairly straightforward though can take quite a while.
Our problem was that although we'd traced our freeholder, nobody at the address admitted to having heard of Mr X, but up he popped as soon as he realised there might be money in it, and tried to wangle more. He didn't succeed, but we did have to pay some arrears of ground rent, which he hadn't bothered to claim for some years from the previous owner.