I've seen these spellings as well, and they are almost certainly dialectal variants / misspellings. Remember that in many dialects to this day, words ending with the "er" sound are pronounced as though they end with "a." (For example, in Australia Taylor and Tayla are indistinguishable). And in a few dialects, words ending in "a" can sound like they end with "er" (in New England you might hear "idea" said as "idear.")
Add up all the confusion and it's easy to see why some possibly less educated parents of the time would write these names with an "-er" ending.
In regards to Leah/Lear and Etha/Ether, I think they are certainly possibly, but I gave a cursory look at the SSA data and didn't see either. I think Ether is unlikely because Etha itself was such an unusual name (only 9 occurrences in 1880). For Leah, the fact that it is a biblical name and would have been familiar to many people in that precise spelling (with the -ah ending that makes it clear there is no R there!), would make it less liable to variation.