I search the IFHF's online database at ROOTSIRELAND.IE. It has abt 20 M church, civil, census, etc B/M/D records for MOST Irish counties. Records before 1863 are increasingly sparse - almost non-existant by 1800. From the sound of the names and link to Scotland, your ancestors were likely protestant. Protestant records are the least likely to have survived.
For George McLeod B 1800 +/- 4 yrs, somewhere in Ireland, with the parents' names unknown, (a very broad search) I found 0 records.
For a Robert McLeod and F Liddle marriage, 1798 +/- 2 yrs, somewhere in Ireland, I found 0 records.