Here's a cover gallery of my complete collection of Page Publications' Omega the Unknown:
Omega the Unknown #1, c.late 1977
Omega the Unknown #2, 1979
Omega the Unknown #3, 1980
Omega the Unknown #4, 1980
Omega the Unknown #NN, c.1982
The first two issues are regular/magazine-sized, and the rest are digest-sized.
As per the covers, #1 was recycled twice.
There may be more Omega issues published by Yaffa. I note there are no 'tall' digest editions, no reprints of #'s 2 and 3, and no recycled and retitled editions in this set.
Each issue reprints three stories from the US series. This means there is one US issue unaccounted for in the Yaffa series. So, there is scope for a 1981 'tall' digest edition with some miscellaneous backup features. However, if this has been published by Yaffa, my guess is it is more likely to lurk as backup feature in another title.