All those articles are about absentee ballots which absolutely nobody in DC is trying to stop entirely. It is how deployed military persons vote. Trump and the republicans are trying to stop States from implementing state-wide voting, or expanding absentee ballots for all citizens which more states are trying to implement due to a friggin’ pandemic. And yes, every system will have people that try to mess with it. But as Oregon’s nearly 2 decades of state-wide-vote-by-mail demonstrates, voting by mail is no more problematic than any other method of voting and it is more convenient for voters.
It's a thing that actually happens:
https://www.nbclosangeles.com/news/local/cudahy-officials-co...
https://www.dothaneagle.com/news/crime_court/woman-convicted...
https://www.stltoday.com/news/local/metro/cahokia-village-tr...
There are also even more small time cases like this:
https://gvwire.com/2019/08/23/mexican-man-who-supports-trump...
Where it's only one person voting when they're not eligible. Those cases often aren't even prosecuted, but at scale it adds up.